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- Rene Descartes
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Physics Conference Room, SB B326
Coffee starts at 12:00 PM and talk starts at 12:15 PM
28
Mar '20
Ksenia Dolgaleva  -  Saturday, March 28, 0020
TBA
University of Ottawa
9
Sep '02
Professor Robert Beserman  -  Monday, September 9, 2002
23
Sep '02
Valery Milner  -  Monday, September 23, 2002
PDFDownload PDF talk time11:00 am
ABSTRACT: Until recently, the field of nonlinear, and generally chaotic, dynamics of billiards (i.e. particles or waves bouncing between sharp reflecting walls) developed separately from the area of atomic physics. Recent achievements in laser cooling and manipulating of atoms made it possible to "play pool" with neutral atoms, creating a new testing ground for classical and quantum chaos. Understanding the dynamics of chaotic billiards with novel properties, such as inter-billiard collisions or moving billiard walls, may prove useful in exploring new ways of controlling atoms and photons. In this talk, I will discuss the "proof of principle" experiments, and possible future directions of research in this new and exciting field.
NOTES: Starts at 11:00 AM
7
Oct '02
Bart van Tiggelen  -  Monday, October 7, 2002
Magneto-optics of chiral media
CNRS/ University of Joseph Fourier, Grenoble
28
Oct '02
Premala Chandra   -  Monday, October 28, 2002
6
Nov '02
Tineke Thio   -  Wednesday, November 6, 2002
18
Nov '02
Dr. Alexander Iomin   -  Monday, November 18, 2002
25
Nov '02
Jonathan Sokolov   -  Monday, November 25, 2002
DNA motion at and near surfaces
Material Science, SUNY at Stony Brook
2
Dec '02
Konstantin K. Likharev   -  Monday, December 2, 2002
Future opportunities for nanoelectronics
Department of Physics, SUNY at Stony Brook
ABSTRACT: The talk will be based on the recent paper [1]. I will give a brief review of the recent research and development of ultrasmall electron devices, including nanoscale field effect transistors (FETs), single-electron transistors (SETs), and some other new devices and nanometer-scalable memory cell concepts. It will be argued that nanofabrication permitting, silicon FETs can be scaled down to ~3 nm gate length, although sub-5-nm devices would be extremely sensitive to random fabrication spreads, and their power consumption would grow very significantly. So far no other device, comparable with the FET in universality, has been found for sub-3-nm operation so far. For example, single-electron transistors, which are scalable to atomic size (below 1 nm), suffer from low voltage gain and high sensitivity to single charged impurities. However, there are several promising ideas for terabit memories and electrostatic data storage, and some exciting prospects of using hybrid SET/FET circuits in new architectures for advanced information processing, including self-evolving neuromorphic networks.
[1] K. Likharev, in: H. Morkoc (ed.), Advanced Semiconductor and Organic Nano-Technologies, Pt. 1, Academic Press (2002)
9
Dec '02
Patrick Huggins   -  Monday, December 9, 2002
18
Feb '03
P. G. Silvestrov  -  Tuesday, February 18, 2003
Adiabatic quantization of Andreev levels
Instituut-Lorentz, Leiden, The Netherlands and Budker Institute of Nuclear Physics, Novosibirsk, Russia
PDFDownload PDF coffee time2:00 pm talk time2:00 pm
ABSTRACT: The problem of finding a semiclassical spectrum of an Andreev billiard (ballistic chaotic cavity coupled to superconductor by an N-mode construction) is considered. We identify the time T between Andreev reflections as a classical adiabatic invariant. Quantization of the adiabatically invariant torus in phase space gives a discrete set of periods Tn, which in turn generate a ladder of excited states. The largest quantized period is given be the Ehrenfest time, proportional to the logarithm of the Plank constant. The wave functions of Andreev levels fill the cavity in a highly nonuniform "squeezed" way, which has no counterpart in normal state chaotic or regular billiards. The theory is applied to the problems of calculating a hard gap in the semiclassical spectrum and crossover between semiclassical and random matrix description of Andreev billiards. Similar ideas may be used for the description of classical to quantum crossover in shot noise in a ballistic quantum dot.
NOTES: Starts at 2:00 PM. Room: B-137
24
Feb '03
Dan Greenberger   -  Monday, February 24, 2003
ABSTRACT: Bell's theorem is a statement that quantum mechanics produces special (entangled) states that have correlations that no local, realistic theory can possible reproduce. Both experimental and theoretical works on Bell's theorem proceed from the idea that the two entangled states are produced by the decay of a single central particle into two particles. But there is a new way to produce entangled states that originates from two independent pairs of particles, and which is exceedingly hard to get a handle on classically. I will discuss the background of the subject, and the new information provided by these new experiments
17
Mar '03
Isa Zharekeshev   -  Monday, March 17, 2003
Level Statistics at the Anderson Transition
Ruhr University of Bochum, Germany
19
Mar '03
Emilio Mendez   -  Wednesday, March 19, 2003
31
Mar '03
Mikhail A. Vorontsov   -  Monday, March 31, 2003
Imaging in Turbulent Environments
US Army Research Laboratory
14
Apr '03
Hui Cao   -  Monday, April 14, 2003
Lasing in Random Media
Northwestern University, Chicago
28
Apr '03
Richard Liboff   -  Monday, April 28, 2003
Origin of the Solar System
Cornell University, Ithaca
5
May '03
Jonathan Sokolov   -  Monday, May 5, 2003
12
May '03
Marilyn Gunner   -  Monday, May 12, 2003
15
Sep '03
Cherice Evans   -  Monday, September 15, 2003
25
Sep '03
Carl Patton  -  Thursday, September 25, 2003
High frequency microwave materials and applications
Colorado State University, Dept. of Physics
NOTES: Thursday
7
Oct '03
Vladimir Chaldyshev   -  Tuesday, October 7, 2003
Engineering of As nanoclusters in GaAs
Brooklyn College, Dept. of Physics
NOTES: Monday Schedule
20
Oct '03
Alexander Abanov   -  Monday, October 20, 2003
27
Oct '03
Viktor Podolskiy   -  Monday, October 27, 2003
ABSTRACT: The optical response of the nanostructured metallic composite could be dramatically different from the response of bulk metal due to resonant excitation of plasmon polariton modes. The spectral characteristics of these modes are strongly affected by the geometry of composite.

In random metal-dielectric percolation films plasmon modes are localized in subwavelength areas with spatial dimensions about 100 nm, so-called "hot spots". Resonant excitation of such localized modes leads to huge enhancements of local linear and nonlinear fields. Due to random structure of the percolation composite, such field enhancement exists in the broad spectrum range, from near UV to mid-infrared, opening a way to the important applications in spectroscopy, biophysics and related areas.

Excitation of polariton modes in composite of metal nanowire pairs, leads to the possibility of construction of left-handed media in the optical and near IF frequency range. One of the most promising applications is the construction of "perfect" lens with subwavelength resolution in the far field.
3
Nov '03
Patrick Sebbah   -  Monday, November 3, 2003
Wave propagation in active and nonlinear random media
University of Nice/CNRS, Dept. of Physics, France and Queens College
10
Nov '03
Evgenii Narimanov   -  Monday, November 10, 2003
Light in asymmetric dielectric resonators: chaos, tunneling and localization
Princeton University, Dept. of Electrical Engineering
ABSTRACT: Dielectric cavities can support long-lived resonant states of the electromagnetic field. These resonances correspond to ray trajectories, which are trapped inside the cavity by internal reflection, as e.g. in "whispering gallery" resonances of microspheres and microcylinders. When such cavities are deformed from their symmetric shapes, the dynamics of the corresponding ray trajectories undergoes a transition from integrability to chaos. This transition has a dramatic effect on the properties of the high-Q resonances.

Microcylinder lasers based on such asymmetric resonators, show strongly directional light emission and high power output (with several orders of magnitude enhancement compared to standard microdisc lasers). Measurements of the optical spectra in these novel semiconductor devices show direct signatures of the classical Kolmogorov-Arnold-Moser transition from integrability to chaos, chaos-assisted tunneling, dynamical Anderson localization and a laser action on "scar"-modes.
17
Nov '03
Bala Sundaram   -  Monday, November 17, 2003
Billiard Dynamics: Cold atoms to lost Whales
College of Staten Island, Dept. of Physics
8
Dec '03
Tony Heinz   -  Monday, December 8, 2003
Terahertz time domain spectroscopy
Columbia University, Depts. of Physics and Electrical Eng.
9
Feb '04
Lior M. Burko   -  Monday, February 9, 2004
ABSTRACT: The two great mysteries of gravitational physics are the fate of the Universe, and the fate of an astronaut who falls into a black hole. Whereas significant progress has been made recently towards resolving the former mystery (the runaway Universe), the latter suffers from an inherent difficulty: by definition, no observations of the interior of a black hole can be made! I will use Einstein's general relativity to argue that the two seemingly unrelated mysteries are intimately linked. In particular, the question of whether black holes can be used as portals for hyperspace travel (allowing particles - and astronauts - to reemerge from a black hole into a remote part of the Universe, or even another Universe) depends on the cosmological parameters, and in particular on the nature of dark energy. I will also argue that the quantum gravity description of the singularity inside the black hole is perhaps not as crucial for this question, and that emergent classical phenomena might be sufficient to determine the fate of an astronaut embarking on this singular odyssey.
11
Feb '04
Valery Milner   -  Wednesday, February 11, 2004
ABSTRACT: Interest in wave propagation in random medium has been constantly growing due to the increasing number of wave objects that can be propagated and studied in random environments. This includes acoustic waves in the Earth's mantle, electromagnetic waves in disordered dielectrics, electrons in quantum dots, and Bose-Einstein condensates in optical potentials. In this talk, two apparent extremes of wave propagation in random media will be discussed and related on the basis of the overarching physical principle governing their behavior - Anderson localization. First, I will present the latest developments in the field of random lasing, in which the localization of photons in random and quasi-periodic structures results in lasing action, which ordinarily is suppressed by disorder. Then, the great potential of using photons as the building blocks of random and periodic media, rather than being exclusively the propagating entities, will be discussed. I will consider the example of the localization of cold atoms in random photonic structures created by light. The advantages and future directions of research along these complementary approaches to the photonics of random and periodic media will be outlined.
18
Feb '04
Dr. Igor L Kuskovsky   -  Wednesday, February 18, 2004
ABSTRACT: Nanophotonics, dealing with optical science and technology at nanoscale, is an exciting new frontier, which provides numerous opportunities both for fundamental research and new applications. Quantum dots (nanocrystals) and nanowires are among the most important building blocks of nanophotnic devices. Therefore, the understanding of underlying fundamental physical phenomena in such structures is very important for future progress in the field.
Mainly two approaches are used to fabricate nanostructures: colloidal chemistry and self-assembly during epitaxial growth. Self-assembled nanostructures are generally divided into two categories, depending on their band alignment: type-I and type-II. We thus present our recent results on both types of quantum dots (QD) and discuss the differences in their optical properties. Moreover, using unique properties of type-II QDs we shall show that there is a smooth transition from isoelectronic centers (few-atom systems) to quantum dots, shedding light on the validity of scaling laws in the "small" size range.
Next, we consider colloidal ZnO nanowires that attracted much interest recently for near-UV lasing applications. It is interesting that there are few reports, if any, on excitonic quantum confinement in such nanowires. We shall present here very recent results on quantum size ZnO nanowires and discuss the difficulties with observing quantum size effects in this material.
23
Feb '04
Patrik Hoffmann   -  Monday, February 23, 2004
From NEAR-Field Optical probes to 3-D Photonic crystals
Advanced Photonics Laboratory Swiss Federal Institute of Technology, CH-1015 Lausanne-EPFL, Switzerland
ABSTRACT: Optical phenomena below the diffraction limit of light have been challenging scientist with increasing importance since 1930. Photonic band-gap (PBG) structures found a strong applied research interest for telecommunication applications in the last years. PBG's could be used as potential switching and connecting units. Alternatively, PBG structures could be the access to future in-vivo Fluorescence Correlation Spectroscopy (FCS) for biomedical diagnosis, increasing the speed of several orders of magnitude. Pharmaceutical screening could also strongly be improved. The centre of the hardware of such systems is the nano-structured device embedded in connecting functional Microsystems. In this talk we focus on the comparison of flexible nano-structure fabrication methods for research and development and rapid prototyping with parallel processing methods for high throughput nano-optical device fabrication.

Focused Electron Beam (FEB) induced deposition of materials allows the extremely flexible brick by brick growth of a huge variety of structures in a serial process. The minimum "brick" size is of the order of 20 nm, and the surface roughness below 1 nm. The index of refraction of the deposit is predominantly determined by the choice of the chemical precursor and to a much less extend by the physical deposition parameters. Modified Scanning Near Field Optical Microscopy (SNOM) tips of non-spherical FEB deposits of gold nano-composite material allowed measuring frequency shifts in the transmission spectra, consistent with surface plasmon excitation calculations. Realization of photonic band-gap structures will be presented.

Parallel processing by electron beam lithography and deep reactive ion etching (DRIE) or lift-off processes that are well known from microelectronics industry have to be adapted to nano-optics, as the materials and the aspect ratio's differ strongly between the applications. 150 nm thick gold lift-off structures resulted in subwavelength confined enhanced light emission.
25
Feb '04
Dima Mozyrsky   -  Wednesday, February 25, 2004
ABSTRACT: Random Telegraph Signals (RTS) in transport current through a conduction channel of a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) are known to be related to charging and discharging of a single impurity due to electron tunneling between the impurity and the channel. The phenomenon provides a unique example where a single electron tunneling can be explicitly monitored. Recent experiments have shown that the RTS in MOSFETs turns out to be strongly dependent on applied magnetic fields, which offers a possibility to manipulate by a spin of a single electron. The latter possibility is of a primary importance for newly developing areas of research such as spintronics and quantum information processing (AKA quantum computing).

In my presentation I will outline our proposal to detect single spin resonance in the system and will present recent experimental results of our colleagues (at UCLA) based on the proposed scheme. I will also discuss certain theoretical results of our research in the field, which include the explanation of unexpectedly large RTS timescales and anomalous magnetic behavior of RTS systems at low temperatures.
1
Mar '04
Vinod. M. Menon   -  Monday, March 1, 2004
Photonic Integrated Circuits (PICs)
Center for Photonics and Optoelectronic Materials (POEM) Princeton University
ABSTRACT: In this talk, we will describe a photonic integration platform known as asymmetric twin guide (ATG), whereby any combination of waveguides, modulators, couplers, lasers, optical amplifiers, detectors, etc. can be "laid out" on a chip using CAD-based design to meet the requirements of a particular application. The designs are then realized on standard, non-regrown, epitaxial wafers followed by standard semiconductor fabrication processes. The integrated photonic devices have performance equal to discrete components. In this context, we will present our recent results on various monolithically integrated photonic circuits that have been developed in our group like all-optical wavelength converter based on Sagnac interferometer geometry, waveguide photodiode with integrated semiconductor optical amplifier, chip-scale demultiplexer using arrayed waveguide grating with integrated photodiodes, and microring resonators with integrated gain elements. Some novel physical phenomena observed in these integrated devices like non-reciprocity of counterpropagating signals in the Sagnac interferometer and control of quality factor and critical coupling in microring resonators will also be addressed. Finally, we will briefly discuss nano/micron-scale photonic circuits that will have possible applications in quantum information processing.
3
Mar '04
Luis Balicas   -  Wednesday, March 3, 2004
ABSTRACT: The complex interplay between magnetism and superconductivity is a central topic in condensed matter physics due to increasing evidence indicating that unconventional superconductivity (SC) occurs in the vicinity of magnetically ordered states. The experimental observations inspired models proposing "magnetically mediated" SC pairing in the proximity of magnetic quantum-criticality in a variety of systems, ranging from heavy Fermion-intermetallics to high- TC superconductors [1]. In this context, the report  of magnetic field-induced superconductivity (FISC) [2,3] in the magnetic layered organic conductor l-(BETS)2FeCl4 constitutes, perhaps, an unique example of a cooperative interaction between both types of orderings, where field-induced ferromagnetism becomes the essential ingredient for stabilizing SC at low temperatures and at very high magnetic fields in an otherwise antiferromagnetic insulator. Here we will briefly revise the current status of organic superconductivity as well as the discovery and the properties of the FISC state.  We will show that its phase-diagram can be well described in terms of the so-called Jaccarino-Peter effect [4] if the quasiparticle nature of the charge carriers is also taken into account. The resulting phase diagram suggests the existence a 2-D Larkin-Ovchnikov-Farrel-Fulde "textured" superconducting sub-phase which only recently has been claimed to exist in the CeCoIn5 compound [5]. The discovery of FISC in an organic compound has lead to interesting developments in the area of nanotechnology [6] and we suggest that it may lead to technological applications.

[1] See for example, A.V. Chubukov, D. Pines, and J. Schmalian, cond-matt/ 0201140 and references therein.
[2] S. Uji et al., Nature (London) 410 , 908 (2001).
[3] L. Balicas et al. , Phys. Rev. Lett. 87 , 67002 (2001).
[4]V. Jaccarino and M. Peter, Phys. Rev. Lett. 9 , 290 (1962).
[5] H. A. Radovan et al. , Nature, 425 (6953), 51 (2003): A. Bianchi et al. ,Phys. Rev. Lett. 91 , 187004 (2003).
[6] M. Lange et al. , Phys. Rev. Lett. 90 ,  197006 (2003).
8
Mar '04
Maxim Vavilov   -  Monday, March 8, 2004
ABSTRACT: One of the most exciting recent experimental discoveries in condensed matter physics has been the observation of the oscillatory magnetoresistance and the zero resistance of a 2D electron gas subject to microwave radiation. For microscopic understanding of this phenomenon we derive the quantum Boltzmann equation for the two-dimensional electron gas at large values of the filling factor. This equation describes all of the effects of the electric fields on the impurity collision integral, including Shubnikov-de Haas oscillations, smooth part of the magnetoresistance, and non-linear transport. We use this equation to analytically analyze the effect of the external microwave radiation on the electron transport. Particularly, we show that the dominant contribution to the observed oscillatory magnetoresistance originates from the non-equilibrium component of the electron distribution function rather than from the corrections to the matrix elements of electron scattering off disorder due to the microwave field.
10
Mar '04
ABSTRACT: The non-contact, quasi-static technique presented involves biasing the silicon wafer with the gate dielectric by depositing charge (from a corona source) and measuring the surface voltage and surface photovoltage (via illumination) using a Kelvin Probe.

The main parameters of measurement presented are: Equivalent Oxide Thickness (EOT), Leakage Current, Flatband Voltage, Density of Interface Traps (Dit) and Soft Breakdown Field. EOT and Dit measurements were chosen for the metrology of gate dielectrics for manufacturing application. Density of Interface Traps, in particular, is an important parameter for qualification of the interface between the dielectric and the semiconductor.
Dit is very sensitive to interface roughness, presence of intrinsic defects or extrinsic impurities all of which can be attributed to particular technique of the growth of the dielectric, silicon implantation specifics, annealing details etc. Examples of gate dielectrics from recent IBM/Infineon Logic and DRAM technologies will be presented.

Note: This talk is based on the work by the author while at IBM Research Division.
15
Mar '04
Xiodong Cui   -  Monday, March 15, 2004
Contacts in nano-electronics
Columbia University
ABSTRACT: As the dimension shrinks to nanometer scale, contacts between metal electrodes and molecules play a much more important role than those in bulk. Effects of "surface states" could spread through the whole nano-electronics system. Here we discuss (i) How to form electric contacts to single molecules, and (ii) How contacts between single-walled carbon nanotubes (SWNTs) and metal electrodes control the properties of carbon nanotube field effect transistors (NT-FETs).
17
Mar '04
Vladimir Butko   -  Wednesday, March 17, 2004
ABSTRACT: A description of the properties of low dimensional electron gases remains one of the most important and challenging problems in condensed matter physics. I will present electron transport and tunneling measurements on ultrathin, metal films. I will show that in the strong disorder limit a gap emerges in the density of states that is solely attributable to fundamental many body electron-electron interaction effects, i.e. the Coulomb gap.
Interestingly, a quantum metal state can be realized, in otherwise highly insulating films, by suppressing the Coulomb gap via a magnetic field. In the second part of my talk I will describe ongoing research into the properties of the two dimensional electron gas of Field Effect Transistors (FETs) fabricated on high quality organic molecular single crystals.
Practical optoelectronic applications of the molecular organic materials, such as flexible, large-area electronic devices will also be discussed.
12
May '04
Valeriy A.Sterligov   -  Wednesday, May 12, 2004
ABSTRACT: Physics of nanosized structures has grown extensively in a recent past. Nanosized structures are developing very quickly, because many applications in nano-optics, nano-electronics etc. become more realistic in view of possible applications. In this talk will be presented some studies of the optical properties of nanosized metallic particles, organized arrays of empty or metal filled nanopores, ordered mesoporous silica films and colloidal suspensions. These objects were studied by scattering, reflection, and transmission of volume and surface electromagnetic waves.
17
Sep '04
Tom C. Weinacht   -  Friday, September 17, 2004
ABSTRACT: Learning to control molecular fragmentation using tailored laser pulses" Ultrafast laser pulses allow us to view atomic and molecular dynamics with time resolution on the order of 10-14 s. Recent advances in laser technology allow us to tailor the electric field of an ultrafast laser pulse and to amplify the pulse to intensities above the atomic unit of intensity. Intense shaped pulses allow us to move from observing to controlling atomic and molecular dynamics.
I will discuss experiments which use shaped ultrafast laser pulses to control molecular fragmentation. The experiments make use of a Genetic Algortihm to discover optimal pulses for control. Our efforts are focused on trying to understand the physical control mechanisms underlying solutions uncovered by the algorithm. Experiments in progress and future experiments will be discussed.
4
Oct '04
Felix Izrailev   -  Monday, October 4, 2004
Localization in low-dimensional models with a correlated disorder
Los Alamos National Laboratory, Instituto de Fisica, Puebla, Mexico
18
Oct '04
Diederik Wiersma   -  Monday, October 18, 2004
Random lasers as fascinating new light sources
European Laboratory for Nonlinear Optics, Florence
19
Oct '04
Isaac Freund   -  Tuesday, October 19, 2004
Polarization singularities in random fields
Bar-Ilan University, Physics
25
Oct '04
Aklesh Lakhtakia   -  Monday, October 25, 2004
Optical nanotechnology is a PLT sandwich
Penn State, Engineering Science and Mechanics
ABSTRACT: Decreasing feature sizes due to advances in nanotechnology place a premium on careful treatment of phase, length, and time in optics. All three quantities are intermeshed due to morphology at the nanometer length-scale. After examining the characteristics of the responses of columnar thin films and chiral sculptured thin films to optical pulses and beams, the thesis that nanotechnology for optics is a phase-length-time sandwich is put forward.
1
Nov '04
Alexander Meyerovich   -  Monday, November 1, 2004
Quantum Systems with Modulated Interfaces
University of Rhode Island
15
Nov '04
Todd Holden   -  Monday, November 15, 2004
22
Nov '04
Stefan Westerhoff   -  Monday, November 22, 2004
Mapping the high energy universe
Columbia University, Physics
29
Nov '04
Patrick Brock   -  Monday, November 29, 2004
6
Dec '04
Lia Krusin-Elbaum   -  Monday, December 6, 2004
ABSTRACT: An intrinsic feature of Mott insulators is that doping, i.e., changing the particle density, can dramatically affect their properties. I will report on our discovery of charge-doping controlled ferromagnetism at room temperature in self-assembled vanadium oxide nanotubes. By adding either electrons or holes, the initially spin-frustrated nanotubes develop a nearly identical nonlinear ferromagnetic spin response, demonstrating a novel unexpected electron-hole complementarity in the nanotube structures. The underlying picture is that, on doping, the Fermi level is swept through the Mott gap in this multiband strongly correlated system, removing the frustration responsible for the spin-gap. Itinerant carriers under spin control are produced in one vanadium Hubbard band which strongly interacts with other more localized vanadium spins. These findings show a path to new spin-aligned nanoscale building blocks, where the Fermi level sweep can be accomplished by applied voltage.
7
Feb '05
Lev Deych   -  Monday, February 7, 2005
28
Feb '05
Lev G. Mourokh   -  Monday, February 28, 2005
ABSTRACT: Interplay of electronic and mechanical properties of nanoelectromechanical systems (NEMS) has been in the focal point of research interest in recent years. In this talk, after brief overview of experimental realizations of such systems, I will present our analysis of two NEMS structures, a mechanical oscillator coupled to an electrical tunnel junction and a quantum shuttle. The explicit expressions for the oscillator (shuttle) damping/decoherence rate, fluctuations of the oscillator (shuttle) position, and for nonlinear conductance of these NEMS have been obtained on the microscopic basis and their voltage and temperature dependencies have been determined. I will also discuss the applications of these models to description of the tunneling in long molecules and electron transport in manganites. Finally, I will describe the directions of our future projects in this field.
7
Mar '05
Jonathan Spanier   -  Monday, March 7, 2005
Ferroelectricity in Nanowires: Finite-Size Scaling and Screening
Department of Materials Science & Engineering, Drexel Nanotechnology Institute
ABSTRACT: First order phase transitions such as the ferroelectric phase transition play a central role in the functional properties of materials; detailed microscopic characterization of the first-order solid-solid transformation has been difficult, however, because bulk measurements often obscure the crucial importance of the surface and defects. We characterize the size-dependent evolution of ferroelectricity in individual, single-crystalline perovskite nanowires using variable-temperature scanning probe microscopy in ultrahigh vacuum, and without the difficulties of ensemble averaging. The measurements show that the ferroelectric phase transition temperature is depressed as the nanowire diameter decreases, reaching room temperature for 3 nm diameter nanowires. Using a combination of density functional theory calculations, phenomenological Landau theory, and thermodynamic analysis, we propose and discuss a new mechanism for surface charge screening in which ferroelectricity is stabilized and even enhanced in smaller domains.
14
Mar '05
Martin McCall   -  Monday, March 14, 2005
4
Apr '05
Ahmer Naweed   -  Monday, April 4, 2005
ABSTRACT: In recent years, whispering-gallery modes (WGMs) of micrometer-sized dielectric spheres (microresonators) have been used in a number of applications, including cavity quantum electrodynamics, trace-gas and chemical detection, biosensing, and nonlinear optics. A convenient method for exciting these modes is photon tunneling from an adjacent tapered optical fiber carrying the incident laser light. The most useful WGMs propagate in circular paths near the sphere's equator and their evanescent part allows interaction with the surrounding environment. By bringing an additional sphere nearly in contact with an excited microresonator, evanescent mode coupling between the two spheres is realized. Experiments performed with coupled fused-silica microresonators show that interference between co-resonant modes of the two spheres gives rise to spectral features that are analogous to those observed in an atomic ensemble that is driven under coherent quantum interference conditions.
11
Apr '05
Peter Koch   -  Monday, April 11, 2005
Experiments in quantum chaos
New York State University at Stony Brook, Physics
18
Apr '05
Bing Hu   -  Monday, April 18, 2005
2
May '05
Mikhail Erementchouk   -  Monday, May 2, 2005
9
May '05
Joseph Birman   -  Monday, May 9, 2005
19
Sep '05
Dilip Gersappe   -  Monday, September 19, 2005
26
Sep '05
Tsampikos Kottos   -  Monday, September 26, 2005
ABSTRACT: We study the decay of an atomic BEC population N(τ) from the leaking boundaries of an Optical Lattice (OL). For a rescaled interatomic interaction strength λ>λb, self-trapped Discrete Breathers (DB's) are created, preventing the atoms from reaching the leaking boundaries. Collisions of other lattice excitations with the outermost DB's, result in avalanches (jumps) in N(τ) which for λb<λ<λ* follow a scale free distribution P(J=δN)≅1/Jα. A theoretical analysis of the mixed phase-space of the system, indicate that 1<α<3 in agreement with our numerical findings. We point out that although our focus is given to atomic BECs, our results are also relevant in a large variety of contexts, most prominently being the light emittance from coupled non-linear optics waveguides
24
Oct '05
John Albrecht  -  Monday, October 24, 2005
Photonic Crystal Defect Mode Analysis
Force Research Laboratory at Wright-Patterson
ABSTRACT: Photonic crystals, in this case periodic structures of dielectrics, can be used to control light propagation through geometry and dielectric contrast.  An especially attractive application for photonic crystals is to construct localized electromagnetic modes by introducing defects in the periodic structure.  These confined modes could be used as optical resonators, laser cavities being the most obvious application. In this seminar, I will discuss a theoretical approach for calculating the photonic structure of defects in 2D photonic crystals. The central feature of this approach is the construction of a basis set of local vector Wannier functions from the perfect crystal eigenstates. It has been proposed [1] that this basis be used to expand photonic crystal defect states analogous to the famous expansion in linear combinations of atomic orbitals of the electronic structure of the ideal silicon vacancy [2]. These approaches rely on a small number of basis states local to the defect region. In this work, we replace the fourier expansion of the perfect crystal by a real-space description in vector finite-elements. This method allows the computation of the Wannier basis on the same grid used to compute the perfect structure and results in a straightforward defect eigenvalue problem. I will present results that verify the eigenmodes of the crystal and examine the physics of selected defect modes.
[1] K.M. Leung, J. Opt. Soc. Am. B 10, 303 (1993).
[2] G.A. Baraff and M. Schluter, PRL 41, 892 (1978); J. Bernholc, N.O. Lipari, and S.T. Pantelides, PRL 41, 895 (1978).
31
Oct '05
Steven Anlage   -  Monday, October 31, 2005
Near-field microwave microscopy
University of Maryland, College Park
14
Nov '05
Richard Liboff  -  Monday, November 14, 2005
High-field properties of a semiconductor
University of Central Florida
ABSTRACT: A general introduction to elements of semiconductor physics is presented, including discussions of E-k diagrams as well as the four fundamental electron-phonon interactions. The quantum-generalized Boltzmann equation is reviewed and applied to high-field transport in a semiconductor. From this analysis a new kinetic equation for the electron distribution function is derived which includes terms corresponding to the four electron-phonon interactions. In the quasi-classical limit, it is found that the acoustic strain interaction dominates, which gives rise to a reduced kinetic equation. In the steady-state limit this equation yields a second-order nonlinear differential equation for the perturbation distribution. The exact solution of the related nonlinear equation represents a significant new result. The distribution function is a generalized Fermi-Dirac distribution which contains the electric field explicitly and is found to reduce to correct forms in various limits.** The analysis is then extended to Silicon, where `equivalent' intervalley scattering comes into play. Drift velocity obtained from the approximate solution of resulting equations is found to agree with observed values for electric fields up to 105 V/cm. A criterion is described discerning between linear and nonlinear electric field effects. * This research includes results from four publications:
1. Phys. Rev. B34, 7063 (1986)
2. J. Appl. Phys. 62, 177 (1987)
3. J. Appl. Phys. 63, 5363 (1988)
4. Phys. Rev. B40, 5624 (1989)
** This `SL Distibution,' appears in the 4th edition of B. Ridley's book, Quantum processs; in semiconductor.
5
Dec '05
Andrew Shabaev   -  Monday, December 5, 2005
12
Dec '05
Hernan Makse   -  Monday, December 12, 2005
Self similarity of complex networks
Levich Institute, City College of CUNY
6
Feb '06
Devinder Mahajan   -  Monday, February 6, 2006
Advanced Fuels and the Role of Catalysis
SUNY Stony Brook and Brookhaven National Laboratory
27
Feb '06
David Pine   -  Monday, February 27, 2006
Colloidal Atoms & Molecules
New York University
8
Mar '06
Jun Li   -  Wednesday, March 8, 2006
20
Mar '06
Sheng Zhang   -  Monday, March 20, 2006
27
Mar '06
Juan Jose Saenz   -  Monday, March 27, 2006
ABSTRACT: In this work we present a detailed analysis of the metal-insulator crossover based on Random Matrix Theory (RMT) and the scaling approach of Dorokhov, Mello, Pereyra, and Kumar (DMPK) [2] together with exact numerical calculations of different model systems. By using a Monte Carlo technique, we have obtained the exact conductance distribution of the DMPK equation all the way from the metallic to the insulating regimes [3]. In the crossover, P(G) presents a sharp behaviour which is clearly different from that observed in SDW. However, the predictions based on the DMPK are in full agreement with microscopic (exact) calculations when the disorder is uniformly distributed through the wire. For classical waves, the absorption leads to a smooth crossover and the calculated statistical fluctuations of transmittances [3] are in good agreement with microwave experiments [4]. We have also analyzed the correlations between waves transmitted through, and reflected from, random media. Although the intensity and conductance fluctuations are practically independent of the sample length L, the correlations present a strong dependence on the length of the disordered region. In the diffusive regime, the RMT structure of both angular and spatial correlations is in full agreement with that obtained by perturbative diagrammatic approaches [5]. Interestingly, for small lengths, we predict a transition from positive to negative correlations for both angular [6] and spatial [7] correlations. [1] A. Garcia-Martin and J.J. Sáenz, Phys. Rev. Lett. 87, 116603 (2001) [2] P.A. Mello and N. Kumar, Quantum transport in mesosc. systems (Oxford Univ., 2004) [3] L. S. Froufe-Pérez, et. al, Phys. Rev. Lett. 89, 246403 (2002) and to be published [4] Chavanov, A.A., Stoytchev, M., and Genack, A.Z., Nature 404 850 (2000) [5] P. Sebbah, et. al. Phys. Rev. Lett. 88, 123901 (2002) [6] A. García-Martín et. al., Phys. Rev. Lett. 88, 143901 (2002). [7] G. Cwilich, L. S. Froufe-Pérez and J.J. Sáenz, to be published.
3
Apr '06
10
Apr '06
Henry Du   -  Monday, April 10, 2006
24
Apr '06
Charles Keeton   -  Monday, April 24, 2006
ABSTRACT: The gravitational deflection of light provides one of the few direct probes of the mass distributions in distant galaxies. More than 80 examples are now known where the gravitational lensing effect produces multiple images of a distant light source, and these "strong" lenses offer important constraints on the dark matter halos around distant galaxies. Recently, 4-image lenses have been used to study whether dark matter halos are smooth or lumpy. This work provides a crucial test of the nature of the dark matter particle, potentially verifying it to be "cold" (as assumed in the popular Cold Dark Matter paradigm) or revealing it to be warm, self-interacting, or otherwise exotic.
1
May '06
Vladimir M. Shalaev   -  Monday, May 1, 2006
ABSTRACT: Negative-index materials (NIMs) may revolutionize the field of optics. There are no known naturally-occurring NIMs. However, artificially designed materials (metamaterials) can act as NIMs. In this talk I outline recent accomplishments in NIMs for the optical range, where applications for such metamaterials can be particularly exciting.
29
Jun '06
Apostolos Vourdas   -  Thursday, June 29, 2006
8
Aug '06
Stephen Arnold   -  Tuesday, August 8, 2006
Atoms of light as biosensors
Polytechnic University
16
Oct '06
Miriam Rafailovich   -  Monday, October 16, 2006
25
Oct '06
Nader Engheta   -  Wednesday, October 25, 2006
ABSTRACT: Metamaterials are engineered composite media with unconventional electromagnetic and optical properties. They can be formed by embedding sub-wavelength inclusions as "artificial molecules" in host media in order to exhibit specific desired response functions that are not readily available in nature, but physically realizable. These metamaterials have exciting characteristics in manipulating and processing RF, microwave, IR and optical signal information. In my group, we have been investigating various features of these media and have been developing some of the fundamental concepts and theories and modeling of wave interaction with a variety of structures and systems involving these material media. From our analyses and simulations, we have found that the devices and components formed by these media may be ultracompact and subwavelength, while supporting resonant and propagating modes. This implies that in such structures RF, microwave, IR and optical signals can be controlled and reshaped beyond the diffraction limits, leading to the possibility of miniaturization of optical interconnects and design and control of near-field devices and processors for the next generation of information technology. This may also lead to nano-architectures capable of signal processing in the near-field optics, which has the potential for significant size reduction in information processing and storage. Furthermore, the nanostructures made by pairing these media can be compact resonant components, resulting in either enhanced wave signatures and higher directivity or in transparency and scattering reduction. We are also interested in nano-optics of metamaterial structures that effectively act as "lumped nano-circuit-elements". These may provide nano-inductors, nano-capacitors, nano-resistors, and nanodiodes as part of "field nanocircuits" in the optical regimes or optical-field nanoelectronics--, and can provide roadmaps to more complex nanocircuits and systems formed by collection of such nanostructures. All these characteristics may offer various potential applications in high-resolution near-field imaging and microscopy, enhancement or reduction of wave interaction with nano-particles and nano-apertures, nanoantennas and arrays, far-field sub-diffraction optical microscopy (FSOM), nano-circuit-filters, optical data storage, nano-beam patterning and spectroscopy, optical-molecular signaling and optical coupling and interfacing with cells, to name a few
NOTES: Wednesday talk
30
Oct '06
Oleg Maksimov   -  Monday, October 30, 2006
Pulsed laser deposition and molecular beam epitaxy of multifunctional oxides
The Electro-Optics Centers, Pennsylvania State University
ABSTRACT: The unparalleled variety of physical properties of oxides holds tremendous promise for future applications. Oxides exhibit the full spectrum of electronic, optical, and magnetic behavior. For example, insulating, semiconducting, metallic, high temperature superconducting, ferroelectric, piezoelectric, ferromagnetic, and non-linear optical effects are all contained within one structurally-compatible family. Integration of oxides with semiconductor devices is expected to enhance device functionality and can lead to the development of faster, smaller, and more power efficient devices.
Due to the difficulty in customizing the structure of oxides and oxide heterostructures, many useful properties remain undiscovered and unexploited. Numerous attempts to synthesize metastable oxide structures by conventional solid-state techniques have failed. A non-equilibrium growth technique is necessary to stabilize these phases. In our laboratory we use two techniques to grow oxide films and heterostructures.
In the first technique, molecular beam epitaxy (MBE), molecular beams of different metals are generated in the effusion cells pointed towards the heated single crystal substrate. Computer controlled shutters, positioned in front of each of the effusion cells, allows to terminate the flux reaching the sample within a fraction of a second while crystalline arrangement of the surface of the film is monitored by reflective high energy electron diffraction. This provides nanometer-scale layering control and allows us to grow customized structures in which the sequence of atomic layers is changed at will. Thus, the full spectrum of the electronic properties of oxides is combined in novel epitaxial heterostructures. In the second technique, pulsed laser deposition (PLD), a target made of selected elements is ablated with the ultra-violet laser. The plum of material condenses on the single crystal substrate resulting in a thin film growth. Although not as precise as MBE, PLD offers a rapid means of preparing custom-made stacks of single crystal films. Using these techniques we investigate growth of high crystalline quality ferroelectric BaxSr1-xTiO3 films and other members of the Srn+1TinO3n+1 (Ban+1TinO3n+1) Ruddlesden-Popper series. Our final goal is the epitaxial growth of these materials on GaN/SiC heterostructures and demonstration of novel devices such as tunable filters and phase shifters.
6
Nov '06
Jiufeng Tu   -  Monday, November 6, 2006
ABSTRACT: Whether a material is an insulator or a metal (maybe a superconductor) is one of the most fundamental questions in physics. While this question can be easily addressed in three dimensions, the situation in lower dimensions is much more complicated. For example, no metallic phase was predicted theoretically in two-dimension (2D) for many years. Experiments on quasi-two dimensional electron systems have continued to reveal some of the most unexpected and theoretically challenging behavior in condensed matter physics. These phenomena include the pseudogap behavior in underdoped high-Tc cuprates and an apparent metal-insulator transition in dilute 2D electron gases. Such anomalous behavior is widely believed to be rooted in the proximity of these systems to quantum phase transitions. Ultra-thin films have served as model quasi-2D systems for many years. In this talk, I will discuss our recent optical studies of these systems in the frequency domain. Our preliminary THz study has identified a percolation transition at sheet resistance (R) ~ 3 kΩ (in addition to the superconductor-to-insulator transition near R = h/4e2 or 6.44 kΩ), possibly associated with a metal-to-insulator transition. We have proposed a new phase diagram for these ultra-thin films that is similar to the phase diagram of high-Tc cuprates.
13
Nov '06
27
Nov '06
Alexandr Granovski   -  Monday, November 27, 2006
ABSTRACT: Recently, it has been shown that magneto-optical Faraday and Kerr effects, as well as the magnetorefractive effect [1] can be significantly enhanced in magnetophotonic crystals (MPC) due to multiple interference and localization of light (see for review [2]). Besides, the influence of an applied magnetic field on the MPC photonic band structure opens a new way to control and manipulate the flow of light [3,4]. The same is true not only for visual light but in a wide range of spectrum, including near-IR and microwaves. The seminar will focus on some new possibilities to develop tunable by magnetic field optical and microwave devices, based on periodical magnetic structures. After a brief introduction into the field of magneto-optics and magnetophotonics the following recent results will be discussed (i) enhanced magneto-optical properties of magnetic granular alloys and discontinuous multilayers; (ii) the magnetorefractive effect in nanocomposites, manganites and multilayered structures; (iii) diluted magnetic semiconductors Si:Mn and TiO2:Co as magneto-optical materials for tunable MPC; (iv) enhanced magneto-optics due to the Tamm states arising at the interface between MPC and non-magnetic photonic crystal; (v) magnetic superprism effect. 
[1] A. Granovsky, M. Inoue, Journ. Magn. Magn. Mat. 272-276 (2004) E1601.
[2] M. Inoue, R. Fujikawa, A. Baryshev, A. Khanikaev, P.B. Lim, H. Uchida, O. Aktsipetrov, A. Fedyanin, T. Murzina, A. Granovsky, J. Phys. D: Applied Physics, 39 (2006) R151. 
[3] A. Merzlikin, A. Vinogradov, M. Inoue, A. Granovsky, Phys. Rev. A, 72 (2005) 046603.
[4] A. Khanikaev, M. Inoue, A. Granovsky, Journ. Magn. Magn. Mat., 300 (2006) 104.
4
Dec '06
Alexey Vinogradov   -  Monday, December 4, 2006
Meta-optics
Institute for Theoretical and Applied Electrodynamics, Moscow, Russia
11
Dec '06
Dr. Ping-Chuan Wang   -  Monday, December 11, 2006
ABSTRACT: Over the last few decades with more and more devices have been required on integrated circuit (IC) chips, the dimensions of these devices have been reduced dramatically.  As the density of IC devices is increased, the fabrication of circuit elements meeting both performance and reliability requirements become ever more challenging. 
Eectromigration, as one of the major reliability challenges, is the transport of matter in a conductor as a result of momentum transfer from electrons to atoms, and it was first recognized as a failure mode in microelectronics in the late 1960's [1].  As a result of this phenomenon, voids are formed at the cathode end of a conductor wire and cause open-circuit; while extrusions can occur at the anode end to cause short-circuit.
In this seminar, electromigration will be explained from a material science point of view.  Methods of engineering materials and structures to enhance the electromigration reliability in product lifetime will also be introduced.

[1] I. A. Blech and H. Sello, "The Failure of Thin Aluminum Current-Carrying Stripes on Oxidized Silicon," Physics of Failure in Electronics, edited by T. S. Shilliday (USAF Rome Air Development Center Reliability Series Proc. Vol. 5, Rome, NY, 1967), p. 496.
5
Feb '07
Eugene Kogan   -  Monday, February 5, 2007
ABSTRACT: A simple quantum mechanical model consisting of a discrete level Resonantly coupled to a continuum of finite width, where the coupling can be varied from perturbative to strong, is considered. The particle is initially localized at the discrete level, and the time dependence of the amplitude to find the particle at the discrete level is calculated without resorting to perturbation theory. The deviations from the exponential decay law, predicted by the Fermi's Golden Rule, are discussed.
26
Feb '07
Lucas Illing   -  Monday, February 26, 2007
ABSTRACT: Time-delayed feedback occurs in many systems and is particularly important at high-speeds, where the time it takes signals to propagate through the device components is comparable to the time scale of the fluctuations. A fascinating feature of such systems is that seemingly simple devices can show exceedingly complex dynamics. This has motivated the use of electronic and photonic time-delay feedback devices in practical applications of chaos, such as ranging and synchronization based chaos communications, for which microwave and radio-frequency oscillators are needed. I will give an overview of our recent work on high-speed chaos generators, synchronization, and chaos communication.
28
Feb '07
Gleb Yushin   -  Wednesday, February 28, 2007
Carbide Derived Carbon
Drexel University
ABSTRACT:    Large surface area and adjustable internal surface chemistry of porous carbons are attractive for a wide range of applications, including electrical energy storage, catalyst support, gas separation membranes, hydrogen storage media, adsorption and separation of biomolecules. Major efforts have been directed towards control of carbon structure, pore size, shape and uniformity, specific surface area (SSA) and total pore volume of these materials.
   Carbide derived carbons (CDC), produced by selective etching of metals from metal carbides, have up to 80% open pore volume and finely tunable pore size and SSA. This is achieved by "burning out" the metals (and metalloids) in halogen atmospheres at modest temperatures. The resulting carbon retains the original shape of the carbide and shows linear reaction kinetics, allowing conversion of a carbide surface to a carbon layer of any thickness, including the entire monolith, film or particle. Depending on the synthesis conditions, the process allows formation of nanotubes, onions, nanocrystalline diamonds, and nanoporous carbons with a remarkably narrow pore size distribution. The ability of the developed technology to fine tune the pore size, and independently control the microstructure and surface termination in carbon, offers unique opportunities for fundamental studies of adsorption and transport in porous media.
   This presentation will provide an overview of the state of the art in the CDC synthesis and describe major breakthroughs in energy and biomedical applications, such as hydrogen storage, electrical energy storage, and adsorption of proteins achieved by rational design of carbon materials.
5
Mar '07
ABSTRACT:    Silicon Microphotonics is a planar integrated technology for adding optical interconnection and enhancing the signal processing capability of microelectronic chips, using the CMOS fabrication toolset. This talk will present the vision of this emerging technology and primarily focus on a critical roadblock: the absence of a silicon compatible, high quantum efficiency material with light emission in the l~1 mm wavelength range.
   Two methodologies for dealing with this materials constraint will be introduced: (i) the design and predicted performance of an ultrahigh gain-efficiency Erbium-doped waveguide optical amplifier, designed to boost the signal power of an on off-chip laser; and (ii) the design and predicted performance of an Erbium-doped ring resonator on-chip laser.
   Materials studies in high concentration Erbium-doped glasses, such as silicon nitride and silicon oxynitride, will be presented for approaches (i) and (ii). We report record optical constant values for SiON:Er and Si3N4:Er, and map the influence of the nitride environment on Er optical gain. Si nanostructures have been observed and characterized for optical sensitizer properties. Current impediments with these materials towards the realization of a lasing cavity will be identified.
   The talk will conclude with recent work on silicon nitride/oxynitride photonic crystal structures for the design of simpler optically pumped waveguide amplifiers, and a passive device application for chip-to-optical fiber coupling of a light signal.
7
Mar '07
Hector Arce   -  Wednesday, March 7, 2007
ABSTRACT: Stars form deep inside clouds of dense dust and gas. Most of the optical light from the nascent stars cannot escape from these clouds, making the star formation process practically invisible to even the most powerful optical telescopes. It was not until recent advances in radio, millimeter, and infrared detectors, over the last 30 years, that important observational progress was made in our understanding of the star-formation process. However, much more progress is needed.
Understanding the star formation process is essential to astrophysics,as it will give us an insight on how the Earth and Sun formed, and will also help us better understand the early universe and the formation of galaxies. I will talk about one of the most important, and yet still poorly understood, stages of the star forming process --the mass outflow stage. As stars form inside molecular clouds, they gravitationally gather gas from their surrounding gaseous environment and disk, while at the same time they energetically spurt out vast amounts of mass in a bipolar flow. Outflows deposit energy and momentum into their surroundings and have a considerable impact on the dynamics, distribution, and chemical composition of the gas in star forming clouds. I will discuss the physical and chemical impact outflows have on the star formation environment.
12
Mar '07
Michael Zamkov   -  Monday, March 12, 2007
ABSTRACT: FORMATION OF TUBULAR ELECTRONIC STATES AROUND CARBON NANOTUBES.
Using two-color photoelectron emission we can populate and subsequently observe the special group of electronic states with wave functions enclosing a carbon nanotube. These cylindrical "electronic rings" constitute a new class of "image" states due to their quantized angular motion. The electron rotation about the axis of the nanotube gives rise to a centrifugal force that virtually detaches the electron charge-cloud from the tube's body. By experiencing the lattice structure parallel to the tube's axis these rings can act as powerful scanning probes of nanotube electronic properties. 
PHOTOCHEMISTRY OF NANOENERGETIC MATERIALS. 
Mixing of reactants on the nanometer length scale represents a new frontier for energetic materials, providing an increased performance in terms of energy release, stability, sensitivity and mechanical properties. Our group is exploring new ways for optimizing these nanoenergetic materials, by using novel fabrication and optical characterization approaches. Specifically, we incorporate metal nanoparticles coated with an inert oxide layer into thin films of a polymer. This mixture exhibits high potential for an efficient conversion of photoenergy into heat or mechanical energy. The dynamics of chemical changes in investigated systems is monitored in real time through time-resolved vibrational spectroscopy.
16
Apr '07
William Rossow   -  Monday, April 16, 2007
The cloud problem in climate change
Electrical Engineering and National Oceanographic and Atmospheric Administration/CREST, City College of CUNY
23
Apr '07
Valery Milner   -  Monday, April 23, 2007
ABSTRACT: Contrary to the common belief that noise and decoherence are detrimental to spectroscopic measurements, we propose and experimentally demonstrate a new method of coherent Raman spectroscopy with spectrally broad incoherent laser pulses. Laser induced molecular vibrations are probed by femtosecond laser pulses with intentionally introduced spectral phase noise, and the vibrational resonances are identified through intensity correlations in the noisy spectrum of the scattered photons. Spectral resolution is not limited by the pulse bandwidth, and is not sensitive to the temporal profile quality of the pulses. The method does not require complicated pulse-shaping setups, spectral multiplexing or spatial beam arrangements. It enables full utilization of the broad bandwidth of femtosecond pulses, and quick scanless retrieval of Raman spectra.
27
May '07
Greg Boutis   -  Sunday, May 27, 2007
ABSTRACT: Q space Nuclear Magnetic Resonance imaging is a well-known non-invasive experimental technique allowing for structural investigations of a variety of complex systems relevant to problems in industry, material science and biology.  The technique allows one to accurately measure the morphology of a confining pore and molecular diffusion rate of mobile molecules within interstices of a structurally complex system. In our laboratory we have recently designed a variable temperature NMR microscope capable of delivering gradient pulses on the order of 50,000 G/cm allowing for high resolution (less than 1 micrometer) scattering studies. In this work we apply this hardware to study the rate of molecular diffusion of water in purified bovine nuchal ligament elastin.
Elastin is an insoluble and highly cross-linked protein in the extra cellular matrix responsible for the elastic properties of vertebrate tissues. While all models for elasticity require water as a plasticizer, no direct experimental study of the molecular dynamics of water has yet been performed. In this talk I will discuss q-space imaging, the measurements we performed, and the implications of our findings.
10
Sep '07
Michael Blanton   -  Monday, September 10, 2007
ABSTRACT: Modern astrophysical observations of the cosmic microwave background, of distant supernovae, and of the distribution of galaxies on very large (billion lightyear) scales has revealed that the Universe is 13.7 billion years old, that the mass in the Universe is mostly in some non-baryonic form ("dark matter"), and that the expansion of the Universe is accelerating due to some unknown physical effect (denoted "dark energy" for convenience). I will discuss this evidence, concentrating on the large-scale distribution of galaxies. In particular, I will discuss the recent detection by the Sloan Digital Sky Survey of the "baryonic acoustic oscillation," the remnants of sound waves in the very early Universe. Finally, I will discuss the prospects for improving our understanding of cosmology by mapping the baryonic acoustic oscillations more precisely and at larger distances.
21
Sep '07
Alexandr Granovski   -  Friday, September 21, 2007
24
Sep '07
Guillaume Bal   -  Monday, September 24, 2007
Imaging in random media and kinetic models
Applied Physics & Applied Mathematics, Columbia University
ABSTRACT: Consider the imaging of inclusions buried in heterogeneous media (modeled as random media) from wave field measurements. For strongly disordered random media, classical imaging techniques based on the back-propagation of coherent wave fields are bound to fail when the random media are not known explicitly. Our only hope then rests on our finding a macroscopic model for the random clutter.

I will argue that kinetic equations offer the simplest models to quantify available observables of wave propagation in such random media, namely, wave energy densities and field-field correlations. Moreover, these observables are asymptotically statistically stable quantities, i.e. do not depend on the realization of the random medium. Buried inclusions then become constitutive parameters in the kinetic equations and their imaging becomes a deterministic inverse transport problem.

I will consider several kinetic-based imaging scenarios depending on available measurements (wave energy measurements or field-field correlation measurements). Their theoretical imaging capabilities will be compared for small-volume inclusions. I will present some reconstructions based on numerical simulations as well as on experimental measurements.
1
Oct '07
Marina Milner-Bolotin   -  Monday, October 1, 2007
ABSTRACT: It is well documented that a significant number of American and Canadian high school and college graduates are scientifically illiterate and have very little interest in science or mathematics. Moreover, their attitudes toward science are often negatively affected by traditional physics instruction. Physics faculty have been trying to address this problem with variable success for the last few decades.  However, proposed solutions (often working on a small scale at upper level courses) were difficult or impossible to implement in large introductory physics courses. The talk will describe how recent findings in Physics Education Research coupled with the effective use of modern technology (Logger Pro and clickers) have been used to implement physics education reform at two large research universities across Canada: The University of British Columbia (700 student-undergraduate introductory physics course for science majors) and Ryerson University (400-student introductory physics course for science majors and 150-student introductory physics course for future architects). The design, implementation and evaluation of Interactive Lecture Experiments was our attempt to reform first year physics teaching and learning.
The preliminary results of the study from Ryerson University and research findings from the University of British Columbia as well as future research directions will be discussed.
15
Oct '07
Sergey Vitkalov   -  Monday, October 15, 2007
22
Oct '07
Andrew Rappe   -  Monday, October 22, 2007
NOTES: Joint Chemistry/Physics Colloquium, Remsen 101
29
Oct '07
Yi Gu   -  Monday, October 29, 2007
ABSTRACT: One-dimensional (1-D) nanomaterials in general and semiconductor nanowires in particular have begun to be explored extensively as promising building blocks for high-performance nanoscale devices. Their promises derive in part from expectations of exceptional electronic properties, such as enhanced charge carrier transport characteristics in 1-D. In this context, quantitative characterizations of carrier transport are desirable to substantiate these high expectations and to establish the performance limitations of nanowire-based devices. In addition, quantitative metrics of carrier transport can also be used to quantify the effects of nanowire surface passivation schemes being developed that aim to improve the device performance.

In this talk, quantitative visualization of carrier transport in semiconductor nanowires using a scanning photocurrent microscopy (SPCM) technique will be demonstrated. Specifically, analysis of the local photocurrent maps obtained by the SPCM technique enables the measurement of carrier diffusion length, a critical transport parameter that controls electronic and opto-electronic device performance, for bipolar and unipolar carrier transport processes in intrinsic (undoped CdS) and extrinsic (n-type Si) nanowires, respectively. In addition, the bipolar carrier diffusion length is found to be enhanced as a result of increased carrier lifetime and the electrostatic repulsion when electrons and holes are spatially separated, and this is supported by local transient (nanosecond) photocurrent measurements and photocurrent mapping under various excitation intensities.
5
Nov '07
Chee Wei Wong   -  Monday, November 5, 2007
19
Nov '07
Vladimir Chaldyshev   -  Monday, November 19, 2007
ABSTRACT: The results of study of the optical reflection and contactless electroreflection from a periodic system of multiple GaAs/AlGaAs quantum wells will be presented. The quantum well width was 15 or 20 nm and the barriers were 104 nm thick. In this system, the electromagnetic resonance of the Bragg reflection occurs at the frequency that coincides or is close to the frequency of the exciton-polariton resonance in the wells. The optical measurements were made at various temperatures, angles of the light incidence and polarization. The optical reflection spectra have been found to be a result of the interplay of three different contributions, namely (i) the reflection from the air/semiconductor interface, (ii) the Bragg reflection due to periodic modulation of the background indices of refraction being different for the wells and barriers, and (iii) the resonant reflection from the periodic system of exciton-polaritons in quantum wells. The latter contribution was separately studied by contactless electroreflection technique in the spectral range covering ground states of the heavy-hole and light-hole excitons. A quantitative analysis of the experimental contactless electroreflection line shape has been done along with quantum-mechanical calculations, which revealed the characteristic energies and broadening parameters for different exciton-polariton levels. In particular, the systems of four and thirty two quantum wells exhibit spectral features with the characteristic broadening of 1.8 meV and 2.2 meV at 17 K, respectively. By comparison with theoretical calculations, we discuss the radiative and non-radiative contributions to the total broadening.
26
Nov '07
Anatoly Kuklov  -  Monday, November 26, 2007
Supersolid state of matter
Physics, CUNY College of Staten Island
ABSTRACT: Supersolid state of matter - phase combining properties of crystal and superfluid - was proposed by Andreev, Lifshitz and Chester for crystalline He4 about 40 years ago. However, early experiments have failed detecting such state. Recently,  Kim & Chan at Penn State have observed predicted by Leggett superfluid decoupling in rotational pendulum - so called non-classical rotational inertia (NCRI) of hcp solid He4. This has caused a strong wave of renewed interest to the supersolid state of matter. I will review main features of supersolid, its various theoretical scenarios and will focus on our most recent results obtained by first principles quantum Monte Carlo large scale simulations. Such simulations impose strong constraints on theories of supersolidity and indicate that structural crystalline defects are responsible for NCRI of He4.
3
Dec '07
Sergey Buldyrev   -  Monday, December 3, 2007
Can one understand water anomalies?
Physics, Yeshiva University
10
Dec '07
Mark Stockman   -  Monday, December 10, 2007
ABSTRACT: Nanoplasmonic phenomena are based on resonant excitation of surface plasmons causing highly enhanced and localized optical fields on nanoscale. These nanoscale fields induce a multitude of enhanced optical effects, in particular, surface enhanced Raman scattering (SERS) including single-molecule SERS, enhanced second- and third-harmonic generations, enhanced two-photon electron emission from nanostructured surfaces, and others. There are many existing and prospective applications of nanoplasmonics in nanoprobing, ultrasensitive detection, biomedical monitoring, etc. The talk will include a broad Introduction to the topic and also certain forefront, focus areas based partially on original contributions, including ultrafast, coherent, nonlinear, and stimulated phenomena. Spaser will be one of the focus points of the talk.
4
Feb '08
ABSTRACT: Due to its unique one-dimensional tubular structure, carbon nanotubes (CNTs) have proven to possess extraordinary physical properties and have emerged as one of the most promising candidates to advance core technologies such as IC miniaturization and others. The current focus of global CNT research is, as it has been since the first CNT discovery, to produce CNTs at desired locations with controlled atomic structures, so that further integration into various nanodevices is enabled. Intensely studied for this purpose is catalytic chemical vapor deposition (CVD) which uses transition metal nanoparticles as catalyst and low-temperature dissociation of hydrocarbon gases as carbon source. I will first introduce various techniques we devised, including electrochemical deposition, thin film dewetting, microsphere self-assembly, interference lithography and nanoporous membrane mask, to fabricate catalyst nanoparticles with desired morphology, areal density, periodicity and texture on large scales, and then discuss a plasma-enhanced chemical vapor deposition (PECVD) process to grow vertically aligned carbon nanotubes as centerpieces for applications in optical antennas, photonic crystals, field emission displays and more.
6
Feb '08
Mumtaz Qazilbash   -  Wednesday, February 6, 2008
ABSTRACT: Materials with significant electronic correlations tend to display remarkable and unconventional properties like insulator-to-metal transitions, high temperature superconductivity and colossal magneto-resistance. Many of these exotic properties have defied understanding most likely because the complex interactions in these materials lead to phase segregation on the nano-scale. For example, the driving mechanism for the temperature-induced insulator-to-metal transition (IMT) in vanadium dioxide (VO2) has been debated for several decades. Central to this debate is the relative importance of electron-electron correlations and charge-ordering to the IMT. I report near-field infrared images of VO2 films that directly show coexisting phases in the vicinity of the percolative IMT. In combination with far-field infrared spectroscopy, the new data reveal the Mott transition with divergent optical mass in the metallic puddles that emerge at the onset of the IMT. These results illuminate a new path towards spectroscopic exploration of electronic inhomogeneities in correlated electron systems.
11
Feb '08
Sumanta Tewari   -  Monday, February 11, 2008
ABSTRACT: Multiferroics are materials that display an amazing coexistence and interplay of long range ferromagnetic and ferroelectric orders. The magnetization (ferroelectric polarization) of these materials can be altered by applying an external electric (magnetic) field, such cross-correlations between the electric and the magnetic phenomena leading to intense interest in the possibility of novel magnetoelectric devices. It was observed recently that the multiferroics that show the strongest sensitivity of polarization to an applied magnetic field are non-collinear spiral magnets. The spiral magnetic ordering, in which the local magnetization rotates around a direction in space (pitch vector), spontaneously breaks coordinate space inversion symmetry giving rise to the macroscopic polarization. With hints from the theories of some liquid crystals, which bear a family resemblance to these systems, in this talk I shall develop a Ginzburg-Landau description of this new class of materials. The resulting theory will allow us to explain as well as predict many unusual and outstanding experimental observations.
13
Feb '08
Diyar Talbayev   -  Wednesday, February 13, 2008
20
Feb '08
Andrey Shytov   -  Wednesday, February 20, 2008
3
Mar '08
ABSTRACT: It seems that everywhere one looks as of late one sees new collaborations between unexpected partners to solve interesting problems in Astronomy. The Largest CCD Optical Survey of The Universe (The SDSS) has a query database designed and funded by a Microsoft research group. It's successor (LSST) will have its 30TB/day data processing needs done by Google while Bill Gates and other entrepreneurs contribute to infrastructure costs. I will discuss how such collaborations are made possible today. Then I will focus on how new approaches to Galaxy Photometric Redshift estimation in The SDSS using advanced regression analysis was developed as the result of a collaboration between Astronomers and Computer Scientists at NASA/Ames and Mathematicians at San Jose State University. I will also quickly review the history of regression analysis and give some background on photometric redshift estimation. Time permitting I will demo another joint project from NASA/Ames called viewpoints (http://astrophysics.arc.nasa.gov/viewpoints) Viewpoints can help characterize multivariate data from any discipline, but much of its development took place with the SDSS in mind.
3
Mar '08
Frank Vollmer  -  Monday, March 3, 2008
ABSTRACT: Optical microresonators such as silica spheres exhibit ultra-high quality (Q) factors and small modal volumes which significantly enhance interaction of the optical field with the material. We use this attribute for biosensing, where a single molecule can shift the frequency of a resonant mode. Applications in biology range from label-free analysis of molecular interactions to detection of bacteria and viral particles. Recently, we have also explored a new approach to photon localization in disordered photonic crystal (PhC) structures. We show that the guided modes in line-defect PhC waveguides experience coherent backscattering by superimposed disorder which can lead to Anderson localization. Random optical cavities with Q's ~ 3 x 105 and ultra-small modal volumes were observed and can find applications in optical sensing systems, random nano-lasers and quantum-computing.
10
Mar '08
Gennady Shvets   -  Monday, March 10, 2008
ABSTRACT: Mid-infrared is one of the most important segments of the optical spectrum because it contains the "fingerprints" of most biological molecules. An explosion of near-field techniques (e.g., spectroscopy with sub-cellular resolution, labels-free detection) motivates the development of new sub-wavelength imaging tools. Experimental demonstration of a near-field super-lens in the mid-infrared (around 11 microns) range will be described. The lens is implemented using crystalline SiC films that have remarkable infrared properties: they support surface polaritons with less damping than most metals. Two demonstrations of super-lensing with l/20 spatial resolution will be demonstrated: (a) using FTIR microscopy [1], and (b) by direct near-field probing with NSOM [2]. Both amplitude and phase-sensitive imaging is demonstrated. It is also demonstrated that super-lensing can be used for sub-surface imaging. Applications to biologically-relevant imaging through water in nanofluidic channels will be discussed. In the second half of the talk, I will describe a novel imaging tool in IR/THZ: tapered multi-wire coaxial endoscope. Using a conventional coaxial waveguide (the ultimate sub-wavelength element!) as an inspiration, I will demonstrate how two types of nanoscale imaging applications are enabled: image magnification and radiation focusing. In the first scenario, the tapered wire array acts as a multi-pixel TEM endoscope by capturing a detailed electromagnetic field profile created by deeply sub-wavelength objects at the endoscope's tip and magnifying it for observation. The resulting imaging method is superior to the conventional scanning microscopy because of the parallel nature of the image acquisition by multiple metal wires. In the second scenario, the image of a large mask at the endoscope's base can be projected into a much smaller image at the tip, paving the way to novel lithographic techniques.
[1] D. Korobkin, Y.Urzhumov, and G.Shvets, "Enhanced Near-Field Resolution in Mid-Infrared Using Metamaterials", JOSA B 23, 467 (2006).
[2] T. Taubner, D.Korobkin, Y.Urzhumov, G.Shvets, and R.Hillenbrand, "Near-field microscopy through a SiC superlens", Science 313, 1595 (2006).
13
Mar '08
Lev Mourokh   -  Thursday, March 13, 2008
ABSTRACT: The interplay of electronic and mechanical properties of nanoelectromechanical systems (NEMS) has been a focal point of research interest in recent years. In this talk, after providing a brief overview of the experimental realizations of such systems, I will present our analysis of two important NEMS structures, a mechanical oscillator (cantilever) coupled to an electrical tunnel junction and a quantum shuttle. Explicit expressions for the oscillator (shuttle) damping/decoherence rate, fluctuations of the oscillator (shuttle) position, and the nonlinear conductance of these NEMS have been obtained on a microscopic basis and their voltage and temperature dependencies have been determined. I will also outline my future plans for research in this field, discussing the feasibility of realizing a coherent phonon source using the suspended nanobridges, electron transport in manganites, and electromechanical processes in living objects. In the latter case, a novel bio-inspired system, nanorotator, will be discussed. Towards the end of my talk, I will describe other projects in which I am involved, concerning electrical and optical properties of semiconductor nanostructures.
17
Mar '08
Eric Akkermans   -  Monday, March 17, 2008
Photon localization-crossover and superradiance
Israel Institute of Technology and Yale University
18
Mar '08
Igor Beloborodov   -  Tuesday, March 18, 2008
Artificial Nanosolids
University of Chicago
ABSTRACT: Artificial nanosolids, arrays of nanoscale grains interacting with each other through electron tunneling, offer rich new horizons of novel macroscopic behavior emerging from nanoscale structure and dynamics. Fundamental microscopic phenomena such as Coulomb correlation, disorder and coherence produce dramatically new and programmable bulk behavior when mediated by nanoscale granular structure. Each building block of these new materials can be viewed as a tiny cluster of atoms of metallic, semiconducting or superconducting elements. These clusters are not as small as molecules but not as large as macroscopic objects. I will review our progress made in the last several years in understanding the properties of artificial nanosolids. In particular, I will discuss the following topics:
1) Introduction to physics of artificial nanosolids
2) Novel transport regimes
3) The phase diagram of artificial nanosolids
4) Future opportunities

Reference
I. Beloborodov et al., Reviews of Modern Physics, 79, 469 (2007).
19
Mar '08
ABSTRACT: Multi-nuclear Nuclear Magnetic Resonance (NMR) techniques have been used to investigate the molecular dynamics and structures in ion conducting and polymer materials. Materials studied included various proton and lithium ion conductors that have application in electrochemical devices such as fuel cells and batteries. Also studied were varying concentrations of aqueous solutions of various superacids, the purpose of which was to provide a fundamental understanding of the ions solvation and mobility and how they were affected by acid concentration. Parameters studied included self-diffusion coefficients (D) obtained by the Pulse Gradient Spin-Echo (PGSE) technique, spin lattice relaxation times (T1) obtained by the Inversion Recovery technique, and chemical shifts. These provided information on the translational mass transport, rate of energy transfer between the nuclei and their surroundings, and the local electronic environment surrounding the nuclei, respectively. In addition to this, the development of high-pressure NMR technique and its application to the study of NMR lineshapes of individual polymers and small molecules in polymer will also be discussed.
28
Mar '08
Neer Asherie   -  Friday, March 28, 2008
Understanding protein phase behavior
Physics, Yeshiva University
PDFDownload PDF locationSB B137
NOTES: Joint Physics - Chemistry Colloquium
7
Apr '08
Fred Cadieu   -  Monday, April 7, 2008
ABSTRACT: Before the space age it was widely believed that the neighboring planets would have many similarities with Earth. But after great technological feats, it became appreciated that natural systems are chaotic. This means that seemingly small differences in the initial states of these worlds led to highly divergent subsequent development. An examination of the physics that led to this divergence, casts Earth as a very special place. As a consequence of this divergent behavior life has flourished on Earth but our planet neighbors have yet to exhibit any signs of life.
14
Apr '08
Swapan Gayen   -  Monday, April 14, 2008
ABSTRACT: Optical imaging and detection of targets embedded in highly scattering turbid media is of interest for a variety of biomedical and remote sensing applications. Salient characteristics of laser light, such as, wavelength, polarization, directionality, coherence, short pulse generation, and ability to probe atomic and molecular transitions provide the basis for imaging, detecting, ranging, and characterization of targets. The talk will review our recent research on ultrashort pulse propagation through turbid media, development of approaches for retrieving image information circumventing the deleterious image blurring effects of light scattering, and present some potential applications.
5
May '08
David Crouse   -  Monday, May 5, 2008
Controlling light with plasmonic and photonic crystals
City College, Electrical Engineering
ABSTRACT: The research fields of plasmonic crystals and photonic crystals have been attracting increased interest due to the fairly recent observations of new and unexpected optical characteristics in subwavelength size-scale periodic structures. Structures such as two-dimensional hole arrays in metal films and optical transmission gratings have been researched in spectral regions from the ultraviolet to microwave. In this talk, the ability to control light with these and related structures will be discussed. Starting with a discussion of anomalously large optical transmission in transmission gratings, the surface plasmons and other optical modes in these structures are identified and their roles in producing several interesting optical characteristics are discussed. The phenomena of anomalously large optical transmission, light circulation, light weaving and light trapping in these structures and their applications to optoelectronic and photonic devices will be discussed.
12
May '08
Tarek Saab   -  Monday, May 12, 2008
28
May '08
Professor Adam Heller   -  Wednesday, May 28, 2008
Electrochemistry of Diabetes Management: Lessening the Pain and the Worry
Department of Chemical Engineering, University of Texas, Austin
PDFDownload PDF locationRosenthal Library, 5thFloor, President's Conference Room
ABSTRACT: About 6 billion glucose assays are performed each year by self-monitoring diabetic people. Obtaining the required blood samples was painful until TheraSense, the company founded by Ephraim Heller and Adam Heller reduced the required blood volume to 300 nL, a volume so small that it can be painlessly obtained. The painless assay, based on thin-layer micro-coulometry, is also accurate, because the outcome of the measurement does not does not depend on temperature, viscosity, or activity of the bioelectrocatalyst. TheraSensewas acquired by Abbott Laboratories and the micro-coulometricsystem, named FreeStyle,is available world-wide. With the intent of removing the worry of diabetes, Adam Heller designed a continuous glucose monitoring system, FreeStyleNavigator, in a collaborative project with colleagues at the University of Texasin Austin and TheraSense, then Abbott Diabetes Care. It monitors the glucose concentration amperometrically, the glucose being directly and selectively electro-oxidized on an electrode having a unique bioelectrocatalyst. The catalyst comprises the enzyme glucose oxidaseand an electron-conducting redoxhydrogelelectrically connecting the redoxcenters of the enzyme to an electrode. The turnover of the enzyme is observed as an electrical current. The user replaces the sensor implanted under the skin every five days. The system alerts the user to actual and impending high or low glucose concentrations.
Poster file (pdf)
NOTES: Department of Chemistry and Biochemistry, Queens College of CUNY. Lunch to follow the seminar at The Agora Restaurant.
15
Sep '08
ABSTRACT: Understanding the structure and properties of many useful technological materials and, in particular, functional nanomaterials, has always been propelled by their in-depth studies with advanced TEM/STEM methods of the electron microscopy, trying to address their properties behind determination of atomic coordinates and composition. A brief review of some important materials examined with S/TEM methods (Pd-cluster catalysts, 1D-SbCrSe3 and Nd2Fe14B ferromagnets, InGaAsP based IR-lasers/photovoltaics, Ca3Co4O9 -thermoelectrics) will be presented. Phase imaging and phase microscopy, being developed along with conventional TEM/STEM methods, provide higher level of physical information, since they can probe electrostatic and magnetostatic potentials for magnetic materials, nanoparticles and hetero-structures at nanoscale resolution. Practical use of such methods named as Lorentz phase microscopy (LPM/TEM) and potential applications for novel position-sensitive diffractive imaging (PSDI/STEM) will be outlined.
22
Sep '08
Jonathan Bird   -  Monday, September 22, 2008
ABSTRACT: For many years now, there has been ongoing interest in the manifestations of many body phenomena in the conductance of strongly-confined, one-dimensional (1D) electron systems. One important aspect of this research has centered on the study of the so-called 0.7 feature in the low-temperature conductance of 1D conductors known as quantum points (QPCs). There have been numerous reports in the literature suggesting that the 0.7 feature should be related to some kind of spontaneous spin polarization in the QPCs, which persists even at zero magnetic field. In this presentation, we review the results of our recent work on this problem, in which we make use of coupled QPCs to probe the properties of transport very close to pinch-off. We observe a resonant interaction between two QPCs whenever one of them pinches off, which we believe is associated with the binding of a single spin to the QPC that is pinching off. A phenomenological theoretical model is developed that relates the observed resonance to a tunnel-induced correlation that arises from the interaction between a presumed bound spin on one QPC and conducting states in the other. Building on these ideas, we use this measurement technique to probe the microscopic properties of the bound spin, finding it to be robustly confined and to show a Zeeman splitting in a magnetic field. The spin binding occurs for stronger gate confinement than the 0.7 feature, and we therefore suggest an alternative scenario for understanding the formation of this feature. In this, one considers the evolution of the self-consistent bound state as the gate potential is weakened from pinch off to allow for electron transmission through the QPC. The suggestion of this work is that a QPC may serve as a naturally-formed single-spin system with electrical readout, a finding that may be useful for the development of future generations of single-spin electronics.

J. P. Bird and Y. Ochiai,Electron spin polarization in nanoscale constrictions, Science 303, 1621 (2004).
Y. Yoon, L. Mourokh, T. Morimoto, N. Aoki, Y. Ochiai, J. L. Reno, and J. P. Bird, Probing the microscopic structure of bound states in quantum point contacts, Phys. Rev. Lett. 99, 136805 (2007).

Work performed in collaboration with: Y. Yoon, T. Morimoto, L. Mourokh, N. Aoki, Y. Ochiai, and J. L. Reno
6
Oct '08
Igor Kuskovsky   -  Monday, October 6, 2008
27
Oct '08
Douglas Durian   -  Monday, October 27, 2008
Granular impact cratering
University of Pennsylvania
ABSTRACT: Experiments on the low-speed impact of solid objects into granular media have been used both to mimic geophysical events and to probe the unusual nature of the granular state of matter. Observations have been interpreted in terms of conflicting stopping forces: product of powers of projectile depth and speed; linear in speed; constant, proportional to the initial impact speed; and proportional to depth. This is reminiscent of high-speed ballistics impact in the 19th and 20th centuries, when a plethora of empirical rules were proposed. To make progress, we developed a means to measure projectile dynamics with 100 nm and 20 µ s precision. For a 1-inch diameter steel sphere dropped from a wide range of heights into non-cohesive glass beads, we reproduce prior observations either as reasonable approximations or as limiting behaviors. Furthermore, we demonstrate that the interaction between projectile and medium can be decomposed into the sum of velocity-dependent inertial drag plus depth-dependent friction. Thus we achieve a unified description of low-speed impact phenomena and show that the complex response of granular materials to impact, while fundamentally different from that of liquids and solids, can be simply understood. This work was done in collaboration with Dr. Hiroaki Katsuragi.
3
Nov '08
Charles Liu   -  Monday, November 3, 2008
10
Nov '08
Tsampikos Kottos   -  Monday, November 10, 2008
Avalanches of Bose-Einstein Condensates in Leaking Optical Lattices
Wesleyan University and Max Planck Institute, Goettingen
ABSTRACT: We study the decay of an atomic BEC population N(τ) from the leaking boundaries of an Optical Lattice (OL). For a rescaled interatomic interaction strength λ>λb, self-trapped Discrete Breathers (DB's) are created, preventing the atoms from reaching the leaking boundaries. Collisions of other lattice excitations with the outermost DB's, result in avalanches (jumps) in N(τ) which for λb<λ<λ* follow a scale free distribution P(J=δN)≅1/Jα. A theoretical analysis of the mixed phase-space of the system, indicate that 1<α<3 in agreement with our numerical findings. We point out that although our focus is given to atomic BECs, our results are also relevant in a large variety of contexts, most prominently being the light emittance from coupled non-linear optics waveguides
17
Nov '08
Sheng Zhang   -  Monday, November 17, 2008
24
Nov '08
Jason Fleischer   -  Monday, November 24, 2008
Towards Optical Hydrodynamics
Princeton University
1
Dec '08
Fengnian Xia   -  Monday, December 1, 2008
8
Dec '08
Peer Fischer   -  Monday, December 8, 2008
Chirality at the Nanoscale
Rowland Institute, Harvard University
PDFDownload PDF locationRemsen 105
ABSTRACT: Chirality is important in a variety of chemical, biological, and physical phenomena. I will discuss two new chiral phenomena that we have observed recently. One concerns the dynamics of chiral nanostructures and the other discusses a surprisingly simple way a physicist can realize chirality at the molecular level. The symmetries that physical fields need to have in order to induce chirality will be discussed.
NOTES: Joint Physics/Chemistry Colloquium to be held in Remsen 105
15
Dec '08
Hakan Tureci   -  Monday, December 15, 2008
9
Feb '09
Abraham G. Kofman   -  Monday, February 9, 2009
ABSTRACT: We obtain optimal conditions for violation of the Bell inequality in the Clauser-Horne-Shimony-Holt form, focusing on the Josephson phase qubits. We start the analysis with the ideal case, and then discuss effects of measurement errors and local decoherence. We also consider the entaglement sudden death due to decoherence and show that the survival time for entanglement is generally much longer than for the Bell violation. Finally, we analyze effects of measurement crosstalk on the Bell violation in phase qubits. In particular, we propose a version of the Bell inequality which is insensitive to the crosstalk.
23
Feb '09
Stephen Lyon   -  Monday, February 23, 2009
2
Mar '09
Ioannis John Kymissis  -  Monday, March 2, 2009
ABSTRACT: Organic field effect transistors (OFETs) have been applied to a number of sensing and actuation systems which can take advantage of their low thermal budget and mechanical flexibility. Characterization of OFETs has been, however, a controversial topic because the conduction and transport models are unlike other well understood systems with accepted transport and device models. We have developed a family of techniques for the analysis and characterization of OFETs using a combination of optical and electrical probe techniques grounded in the physics underlying transport in organic semiconductor thin films. These techniques provide unique insights into device performance and also indicate ways to better fabricate and drive devices in practical circuits. These probes include the use of quasi-static charge metrology techniques, spatially and spectrally resolved photocurrent analysis, and the analysis of switching noise in OFET circuits. The physical basis behind these tools, as well as some analytical results which they have yielded in practical devices, circuits, and deliberately doped systems will be presented. The application of OFETs to a number of sensor systems including additive photodetectors and strain sensing will also be presented, along with what these analytical strategies can tell us about better ways to fabricate and drive these devices.
NOTES: COLLOQUIUM CANCELLED DUE TO SNOWSTORM
9
Mar '09
Vadim Oganesyan   -  Monday, March 9, 2009
Many-body localization
College of Staten Island, CUNY
23
Mar '09
Anatoly Smirnov  -  Monday, March 23, 2009
Physics of natural nanodevices: proton pumps and rotary biomotors
RIKEN, Japan, and The University of Michigan, Ann Arbor
ABSTRACT: In the process of respiration a living cell extracts energy from light or from food and converts it to a proton electrochemical gradient across an inner mitochondrial membrane. Mitochondria are small organelles inside the cell, which serve as efficient power plants. On the next stage of the respiration process protons flow back and rotate ATP synthase - a nanomachine using energy of mechanical rotation to synthesize the energy currency of the cell - the ATP molecules. Cytochrome c oxidase (CcO) is an enzyme, which is able to harness energy of food-stuff electrons and pump protons against the transmembrane voltage gradient. Despite the fact that the crystal structure of this enzyme is known in detail, a mechanism of proton pumping is poorly understood. The physical picture of the torque generation and a proton translocation in the rotary biomotor F0 of ATP synthase remains also unclear. In the present talk we apply the methods of quantum transport theory to the above-mentioned bioenergetic problems and develop a simple kinetic model of CcO proton pump. We also propose a theoretical description of the rotary biomotor F0. For realistic parameters the model of the CcO proton pump works with efficiency 95% and reproduces all four experimentally observed kinetic phases of the proton pumping process. The model of the rotary biomotor includes a stator part and a ring-shaped rotor having twelve proton-binding sites. We show that this system can work in three different regimes found in experiments: at low temperatures the loaded motor shuttles protons without producing any unidirectional rotation, whereas at higher temperatures the motor generates a constant torque with efficiency about 80%. Finally, the system works as a proton pump in the presence of a significant external torque produced by ATP hydrolysis.

References:
1. A. Yu. Smirnov, L. G. Mourokh, and F. Nori, Kinetics of proton pumping in cytochrome c oxidase. arXiv:0812.1785 (2008)
2. A. Yu. Smirnov, S. Savel'ev, L. G. Mourokh, and F. Nori, Proton transport and torque generation in rotary biomotors, Phys. Rev. E 78, 031921 (2008).
27
Mar '09
Mitsuteru Inoue   -  Friday, March 27, 2009
Magnetophotonic Crystals
Department Electrical and Electronic Engineering, Toyohashi University of Technology
30
Mar '09
Gerard Ben Arous   -  Monday, March 30, 2009
Slow relaxation in random media
Courant Institute, NYU
6
Apr '09
Chris Johnson Jacobsen   -  Monday, April 6, 2009
PDFDownload PDF locationRemsen 105
ABSTRACT: X-ray microscopes are able to deliver images of micrometers-thick samples at tens of nanometers resolution. I describe new developments which go beyond simple imaging to look at the complexities of real life problems. By analyzing spectroscopic image sequences taken across the carbon absorption edge, one can understand nanoscale heterogeneities in organic chemistry relevant to biofuels materials as well as soil bacteria that act to alter metal toxicity. By combining fluorescence with phase contrast, one can obtain quantitative maps of trace element concentration which provides insights into problems such iron as a limiting factor in CO2 uptake by the oceans. By directly inverting diffraction data one can image cells without the resolution and damage-enhancing inefficiencies of x-ray lenses. These examples illustrate how new capabilities in x-ray microscopy are providing new views of the complex world that complement the capabilities of light and electron microscopy
NOTES: Joint with Chemistry Department
14
Apr '09
Mikhail Erementchouk   -  Tuesday, April 14, 2009
Semiconductor nonlinear optical response
University of Central Florida
20
Apr '09
Carlos Meriles   -  Monday, April 20, 2009
NOTES: Colloquium cancelled due to unforeseen consequences
27
Apr '09
Saskia Fischer   -  Monday, April 27, 2009
ABSTRACT: In this talk I will discuss recent results[1] on ballistic transport and quantum interference in a nanoscale quantum wire loop.Nanolithography is applied to fabricated multi-terminal quantum wire structures from GaAs/AlGaAs field-effect heterostructures hosting a high-mobility two-dimensional electron gas. Four-terminal measurements of current and voltage characteristics as a function of top gate voltages show negative bend resistance as a clear signature of ballistic transport. In perpendicular magnetic fields, phase-coherent transport leads to Aharonov-Bohm conductance oscillations, which show equal amplitudes in the local and the nonlocal measurement at a temperature of 1.5 K and above. We attribute this observation to the symmetry of the orthogonal cross junctions connecting the four quantum wire leads with the asymmetric quantum wire ring.
[1] S.S. Buchholz, et al. APL 94, 022107 (2009).
4
May '09
Luca Dal Negro   -  Monday, May 4, 2009
NOTES: Colloquium has been cancelled
11
May '09
Andrew Baker   -  Monday, May 11, 2009
ABSTRACT: Fully understanding the evolutionary state of a galaxy requires that we characterize its gas reservoir, of which the molecular component represents the mass directly available for star formation.I will discuss radio observations of molecular gas in two populations of star-forming galaxies at high redshift (selected based on their rest-frame ultraviolet and far-infrared emission) and what we can learn from them. I will highlight recent work with the "Zpectrometer" (a new, ultrawide bandwidth spectrometer for the 100m Green Bank Telescope) and prospects for future work with

ALMA (Atacama Large Millimeter/submillimeter Array).
1
Jul '09
Bart van Tiggelen   -  Wednesday, July 1, 2009
14
Sep '09
Ioannis John Kymissis   -  Monday, September 14, 2009
ABSTRACT: Organic field effect transistors (OFETs) have been applied to a number of sensing and actuation systems which can take advantage of their low thermal budget and mechanical flexibility. Characterization of OFETs has been, however, a controversial topic because the conduction and transport models are unlike other well understood systems with accepted transport and device models. We have developed a family of techniques for the analysis and characterization of OFETs using a combination of optical and electrical probe techniques grounded in the physics underlying transport in organic semiconductor thin films. These techniques provide unique insights into device performance and also indicate ways to better fabricate and drive devices in practical circuits. These probes include the use of quasi-static charge metrology techniques, spatially and spectrally resolved photocurrent analysis, and the analysis of switching noise in OFET circuits. The physical basis behind these tools, as well as some analytical results which they have yielded in practical devices, circuits, and deliberately doped systems will be presented. The application of OFETs to a number of sensor systems including additive photodetectors and strain sensing will also be presented, along with what these analytical strategies can tell us about better ways to fabricate and drive these devices.
5
Oct '09
Luca Dal Negro   -  Monday, October 5, 2009
19
Oct '09
Carlos Meriles   -  Monday, October 19, 2009
22
Oct '09
Zoya Leonenko  -  Thursday, October 22, 2009
PDFDownload PDF talk time4:00 pm
ABSTRACT: Scanning Probe Microscopy is a big and growing family of many nanoscale characterization methods which are widely used in many areas including physics, chemistry, biology, biomedical and nano-technology. One of them, Atomic force microscopy (AFM) is a well-known scanning probe microscopy technique which allows imaging and nanomanipulation on a single molecule and nm scale. In this talk I will give introduction to several scanning probe microscopy methods, and focus on Atomic Force Microscopy (AFM), and Kelvin Probe Force Microscopy (KPFM), which we use in my laboratory to investigate complex structure and function of lipid films and lipid-protein interactions. Molecular arrangement of lipids and proteins in monolayer or membrane gives rise to complex film morphology as well as an electrical surface potential or non-uniform charge distribution, which rule many biological processes and diseases. I will give a review of current research projects in my laboratory, such as a) study of structure and function of lung surfactant and how these are affected by cholesterol; b) investigation of amyloid fibril formation which is associated with more than 20 neurodegenerative diseases for which no cure is currently available, for example Alzheimer's and Parkinson's to name a few. We focus on elucidating the role of lipid membrane surfaces in amyloid fibril formation.
26
Oct '09
Myriam Sarachik   -  Monday, October 26, 2009
ABSTRACT: Molecular Magnets, sometimes referred to as single molecule magnets, are organic materials that contain a very large (Avogadro's) number of molecules that are (nearly) identical nanomagnets, providing ideal laboratories for the study of nanoscale magnetic phenomena. With molecular clusters of large total spin 10, Mn12-acetate and Fe-8 are borderline between classical and quantum magnetism. They are magnetically bistable at low temperatures, they exhibit ``macroscopic quantum tunneling'' between up and down spin orientations, and quantum interference between tunneling paths. Interest in these materials has grown dramatically in the last several years, owing to their possible use for high density storage of information, as well as the possibility that some member of this family of materials could provide qubits for quantum computation.
Following an introductory description of the major features that characterize these interesting materials, this talk will focus on the processes by which the large (S=10) magnetization vector of individual molecules in a Mn12-acetate crystal reverse direction - by classical over-the-barrier spin reversal, quantum tunneling (under-the-barrier), or as a magnetic avalanche propagating at subsonic speed through the crystal in the form a narrow front.
2
Nov '09
Ildar Salakhutdinov   -  Monday, November 2, 2009
9
Nov '09
Tsampikos Kottos   -  Monday, November 9, 2009
16
Nov '09
Christopher Gerry   -  Monday, November 16, 2009
Quantum sensing and metrology
Lehman College of CUNY
23
Nov '09
A. Douglas Stone   -  Monday, November 23, 2009
ABSTRACT: Recently invented micro and nano lasers have challenged our understanding of lasers and revealed the absence of a predictive theory. Perhaps most surprising is the existence of random lasers, based on multiple scattering between nanoparticles in the presence of gain. While these lasers behave in most respects like conventional lasers in terms of their emission properties, they have no mirrors or cavity of any kind. and the linear scattering spectrum reveals no long-lived resonances to support lasing. In the absence of long-lived cavity resonances conventional semiclassical laser theory, which assumes such resonances evolve into the laser modes, has no starting point. Recently, we have developed a modern formulation of semiclassical laser theory, which elucidates the nature of lasing modes in cavities of arbitrary complexity and arbitrary leakiness, including the case of random lasers. The theory also treats the strong non-linear interaction between lasing modes to all orders and has been shown to agree with full numerical solutions of the lasing equations with no adjustable parameters. Thus we are in position to understand qualitatively complex and random lasers and in the near future produce a truly predictive theory for many lasers of applied and fundamental interest.
14
Dec '09
Tanya Zelevinsky   -  Monday, December 14, 2009
1
Feb '10
Kostiantyn Bliokh   -  Monday, February 1, 2010
17
Feb '10
Photonics Search Presentation   -  Wednesday, February 17, 2010
To be announced
To be announced
22
Feb '10
Photonics Search Presentation   -  Monday, February 22, 2010
To be announced
To be announced
24
Feb '10
Photonics Search Presentation   -  Wednesday, February 24, 2010
To be announced
To be announced
1
Mar '10
Photonics Search Presentation   -  Monday, March 1, 2010
To be announced
To be announced
3
Mar '10
Photonics Search Presentation   -  Wednesday, March 3, 2010
To be announced
To be announced
8
Mar '10
Photonics Search Presentation   -  Monday, March 8, 2010
To be announced
To be announced
15
Mar '10
Photonics Search Presentation   -  Monday, March 15, 2010
To be announced
To be announced
22
Mar '10
Stephen Holler  -  Monday, March 22, 2010
ABSTRACT: Dielectric microcavities have garnered much interest in recent years to study a myriad of physical phenomena including cavity QED effects, lasing, non-linear processes and sensing. Of particular interest are spherical microcavities which possess a high degree of symmetry and support high-Q whispering gallery modes implicated in a variety of physical phenomena. Whispering Gallery Mode (WGM) resonances are efficient conduits for photon transport and may be used to enhance both linear and non-linear optical processes while simultaneously serving as sensitive probes of the local environment. This presentation will examine the role whispering gallery mode resonances of spherical microcavities have played in our research to elucidate physical phenomena such as intermolecular energy transfer far beyond the Forster range, cavity mode selection as a means for molecular characterization, and fluorescence lifetime modification. In addition, our recent work on ultrasensitive biomolecular sensors has demonstrated an optical tractor beam capable of pulling nano-particles into orbit. This carousel mechanism provides a novel means for particle transport and separation in addition to acting as a tool for surface potential characterization. These advances in microcavity photonics pave the way for a myriad of studies that have the potential to offer new insights into biomolecular systems, result in novel laser and micro-photonic geometries, and enhance Homeland Security and clinical diagnostics through advanced biological and chemical sensor platforms. The broad applicability of microcavity photonic devices to both fundamental and applied areas of research in physics, chemistry, and biology make them truly diverse, interdisciplinary, and important scientific tools.
24
Mar '10
Photonics Search Presentation   -  Wednesday, March 24, 2010
To be announced
To be announced
19
Apr '10
Maria Tamargo  -  Monday, April 19, 2010
ABSTRACT: The thrust of the research efforts at the Molecular Beam Epitaxy (MBE) Lab at CCNY is the development of novel semiconductor nanostructures that offer enhanced materials properties for new device applications and physical phenomena. Two areas on which we have focused during the past few years have been the growth of multi-quantum well structures for intersubband (ISB) devices and the growth of submonolayer type II – quantum dots for enhanced p-type doping of difficult to dope materials. I will describe our recent advances in these two areas. Quantum cascade (QC) lasers are a novel semiconductor laser that relies on ISB transitions. They exhibit many unique advantages over the more typical interband devices, including large independence from materials parameters to tune the emission wavelength, ultra-fast response, and the use of uni-polar structures. In order to reach shorter wavelengths in the IR, which is needed for many sensing applications, we have begun to explore the use of wide bandgap II-VI semiconductors for QC laser applications. We have recently demonstrated QC emission form ZnCdMgSe-based heterostructures, and are actively pursuing lasing. Se-based wide bandgap II-VI's are notoriously difficult to dope p-type, as is the case with many other wide bandgap semiconductors. By contrast, ZnTe is easily doped p-type, while n-type ZnTe is not readily achieved. We recently demonstrated a novel approach by which small doped nanoclusters of ZnTe embedded in a ZnSe matrix produce a new composite material in which p-type doping is enhanced by an order of magnitude compared to that of ZnSe. Other properties, such as band gap of the material are not significantly changed. We have carried out a broad range of experiments to understand the mechanism and elucidate the properties of this new nanocomposite material. Other potential applications, such as photovoltaics, have become apparent from our studies.
26
Apr '10
3
May '10
Yasha Yi   -  Monday, May 3, 2010
ABSTRACT: Nano-scale photonics is one of the key components in future clean renewable energy, which plays the central role in next generation photovoltaics and solar cells. After giving an introduction on the available renewable energy sources on earth, I will talk about next generation solar cells utilizing photonic crystals, and our recent research on optoelectronic properties of composite (structurally designed) materials at nm scale for the applications on energy related materials and devices. Utilizing current microelectronics technology and measurement techniques, it is possible to study these novel energy related materials and devices in ways that were unimaginable a decade or two ago. In order to improve next generation thin film solar cell efficiency(2nd generation solar cell), we have developed a new light-trapping scheme that can tremendously enhance optical path length and make light almost completely absorbed at AM1.5 solar spectrum by using novel photonic materials structure on the backside. It makes incident light strongly bent and reflected almost parallel to the surface of the absorption layer, hence the optical path length can be enhanced more than two orders of magnitude longer than that obtained by conventional light trapping schemes. Furthermore, it provides extremely high reflectivity with large omnidirectional bandgap over several hundred nanometers in the solar spectrum range. As a result, the overall efficiency of the solar cell based on our photonic structure is improved significantly. Lastly, I will talk about many potential challenges and future work to be pursued in clean energy fields that require good control of photons and electrons at nanometer scale. This capability can efficiently convert sunlight energy to electricity and meet our demand for clean and renewable energy in the future.
2
Jun '10
Rajeev Pathak  -  Wednesday, June 2, 2010
ABSTRACT: It is an intriguing question why ordinary matter that interacts through Coulomb 'forces' should remain stable at all and not collapse, unlike its gravitational analogue on the cosmic scale. It turns out that a naive 'explanation' based on the Heisenberg Uncertainty Principle alone turns out to be fallacious! On the other hand, it is the fermionic nature of the electron entailing the Pauli Exclusion Principle that actually endows matter with stability. In this colloquium, following Lieb's monumental work, stability of ordinary matter will be discussed threadbare. Also, an upper bound on the number of bound states for an arbitrary attractive potential will be derived using some simple mathematical inequalities. Once again, following Lieb, an interesting upper bound on the maximal degree of negative ionicity possible will be derived, and impossibility of a neutral atom and positron ever forming, albeit an exotic 'quasi-bound-state', will be established. Stability of polar and non-polar molecules and molecular clusters subjected to high external electric fields will also be examined. While in many cases the external field distorts or decomposes the molecular cluster, in some other selective cases, it can strongly bind two molecules exhibiting an exotic phenomenon of 'field induced covalence'.
9
Jul '10
Matthieu Davy   -  Friday, July 9, 2010
Time Reversal Methods at Microwave Frequencies
Institut Langevin, Laboratoire Ondes et Acoustique, Paris
13
Sep '10
Timothy Paglione  -  Monday, September 13, 2010
Star Formation from the Radio to Gamma-Rays
York College of CUNY, American Museum of Natural History
ABSTRACT: Massive stars are an important driver of much of galaxy evolution. These stars live furiously, greatly affecting their surroundings with their winds and radiation, then die dramatically in giant explosions that enrich the interstellar medium in heavy elements. Their lives are relatively brief as well ("only" 10 million years or less) so their impact is not only profound but immediate. Certain galaxies known as starbursts create numerous clusters of these massive stars in their centers. Starburst galaxies may be studied across all the electromagnetic bands, probing different physical regions and processes, but they are traditionally identified by their radio and infrared emission or optical spectroscopy. I augment these studies by including data from a window only recently opened to us: gamma-rays. The gamma-ray emission effectively ties together nearly the entire spectrum of a galaxy while elucidating the impact of cosmic rays on galaxy evolution.
20
Sep '10
Willam Bialek   -  Monday, September 20, 2010
Critical phenomena and biological networks
Princeton University and CUNY Graduate Center
PDFDownload PDF coffee time11:45 am talk time12:00 pm
ABSTRACT: Most of the interesting phenomena of life emerge from interactions among a large network of more basic units: interactions among amino acids stabilize the structure of proteins, interactions among genes define the states of our cells, interactions among neurons determine our thoughts, and interactions among groups of organisms are responsible for beautiful schools of fish or flocks of birds. For decades, physicists have hoped that these emergent biological phenomena could be described using the ideas of statistical mechanics, but the models that emerged from this work often have been a bit abstract, not so well connected to what can be measured. Recently it has been suggested that one can actually construct statistical mechanics models directly from data on these complex systems, using the idea of maximum entropy. I'll explain how this works, illustrate some of the surprising successes of this approach, and then outline the most surprising development that has come out of this work: many different biological networks seemed to be poised near a critical point in their parameter space. Examples will be drawn from protein molecules, neural circuits, and flocks of birds, and I will point to emerging experiments that will test these ideas much more clearly. I also hope to convey the fun of connecting theory and experiment, physics and biology.
18
Oct '10
Fengnian Xia   -  Monday, October 18, 2010
Graphene Nanophotonics and Nanoelectronics
IBM Thomas J. Watson Research Center
ABSTRACT: Graphene, a 2-dimensional carbon based material system, recently attracts world-wide attention from physicists and engineers due to its unique electronic and photonic properties. In this talk, I will first discuss the historical evolvement of electronics and photonics, followed by the potential of graphene in electronics and photonics. A few important developments in graphene photonics will then be presented, including photocurrent imaging, ultrafast (> 40 GHz) photoresponse, and the application of graphene photodetector in a realistic optical communication link. Next, two approaches to create a bandgap, using lateral confinement in single layer graphene and vertical E-field in bi-layer graphene, will be covered in detail. I will show that a transport bandgap of > 130 meV can be realized in biased bilayer graphene. The developments in graphene bandgap engineering may enable a few important applications, such as graphene digital electronics, electron Veselago lens and graphene spin qubit
1
Nov '10
Ronald Koder   -  Monday, November 1, 2010
8
Nov '10
Roman Kezerashvili  -  Monday, November 8, 2010
Solar sail to test fundamental physics
New York City College of Technology of CUNY
ABSTRACT: The motion of the solar sail is determined by the solar radiation pressure as well as the spacetime geometry. The Pioneer anomaly, which is the unexplained acceleration of the Pioneer 10 and 11 spacecraft on escape trajectories from the outer solar system and the effects of general relativity on a solar sail propelled satellite will be discussed. We present deviations from Kepler's third law for heliocentric orbits near the sun. In particular, we consider deviations in the period of circular orbits due to the spacetime curvature near the sun, frame dragging from the rotation of the sun, and the oblateness of the sun. The Poynting-Robertson effect on a nearly-circular heliocentric trajectory of a solar sail is discussed. In addition, for non-Keplerian orbits which are outside of the plane of the sun, we predict an analog of the Lense-Thirring effect for which the orbital plane precesses around the sun. This can be tested by a solar sail propelled satellite.
15
Nov '10
Michael Shlesinger  -  Monday, November 15, 2010
ABSTRACT: This lecture traces the history of probability theory from the throwing of bones, sticks, and dice to modern times. Early 18th century books, Jacob Bernouill's "The Art of Conjecture" and Abraham DeMoivre's "The Doctrine of Chances" were rich with new mathematics, insight and gambling odds. Progress was often made by confronting paradoxes. The first of these confused probabilities with expectations and was explained in the Pascal-Fermat letters of 1654. The St. Petersburg Paradox involved a distribution with an infinite first moment, and Levy discovered a whole class of probabilities with infinite moments that have found a surprising utility in physics. The Bertrand paradox involved measure theory for continuous probabilities, Poisson discovered that adding random variables need not always produce the Gaussian, and Daniel Bernoulli and D'Alembert argued over the probabilities for the safety of smallpox vaccinations. Using these and other anecdotes, this lecture discusses vignettes that have brought us to our modern understanding of probability theory.
22
Nov '10
Hui Cao   -  Monday, November 22, 2010
ABSTRACT: Wave optics is an old field of physics that has experienced rapid advances lately. Thanks to modern nanofabrication technology, complex nanostructures such as photonic crystals and metamaterials can be fabricated. They display unusual optical properties and phenomena, e.g., photonic bandgaps, negative refractive index, optical magnetism and cloaking. In this talk, I will start with a brief introduction of the field of nanophotonics and then focus on our studies of photonic nanostructures of random morphology. I show how we can trap light in such structures to make random lasers. Next, learning from the color generation by nanostructures in bird feathers, we use short-range order to enhance light scattering and confinement in artificial nanostructures. Finally I will talk about our latest work on coherent perfect absorbers which can be considered as time-reversed lasers
29
Nov '10
Michael Sumetsky   -  Monday, November 29, 2010
ABSTRACT: A slightly nonuniform and even an ideally uniform optical fiber can perform as a high Q-factor optical microresonator which hosts different types of strongly localized whispering gallery modes (WGMs). These modes are described theoretically and observed experimentally. First, it is shown that a very long (translationally symmetric) lossy dielectric optical microcylinder possesses localized modes. The Q-factor of these WGMs is only 2.5 times smaller than the Q-factor of WGMs in a spherical microresonator fabricated of the same material. Next, localization of WGMs in a cone with a small half-angle is demonstrated. The cylindrical and conical modes are found to be common in conventional optical fibers. The developed theory of a these modes is in excellent agreement with experiment. Finally, the cylinder and conical modes are compared with bottle WGMs that were investigated previously.
6
Dec '10
Jacob Khurgin   -  Monday, December 6, 2010
7
Feb '11
Robert Kohn  -  Monday, February 7, 2011
ABSTRACT: Crystalline films are often grown or annealed below their roughening temperature. The microscopic physics involves the attachment and detachment of atoms at steps, and the diffusion of atoms across terraces. The macroscopic consequences of these atomic-scale mechanisms are still poorly understood. My talk will discuss recent progress with Hala Al Hajj Shehadeh and Jonathan Weare, concerning the evolution of a one-dimensional step-train separating two facets in the "attachment-detachment-limited" regime. I'll explain why the evolution is asymptotically self-similar, and why its continuum limit is associated with certain fourth-order nonlinear PDE's. The talk will be self-contained, requiring no prior background about crystal growth.
14
Feb '11
Mordecai-Mark Mac Low  -  Monday, February 14, 2011
The Formation of Molecular Clouds and Massive Stars
American Museum of Natural History
ABSTRACT: In this talk I consider two questions.  First, I investigate the formation of molecular clouds from diffuse interstellar gas.  It has been argued that the midplane pressure controls the fraction of molecular hydrogen present, and thus the star formation rate.  Alternatively, I and others have suggested that the gravitational instability of the disk controls both.  I present numerical results demonstrating that the observed correlations between midplane pressure, molecular hydrogen fraction, and star formation rate can be explained within the gravitational instability picture. Second, I discuss how ionization affects the formation of massive stars. Although most distinctive observables of massive stars can be traced back to their ionizing radiation, it does not appear to have a strong effect on their actual formation.  Rather, I present simulations suggesting that stars only ionize large volumes after their accretion has already been throttled by gravitational fragmentation in the accretion flow. At the same time these models can explain many aspects of the observations of ultracompact H II regions.
16
Feb '11
ABSTRACT: We describe enzymatic systems which involve biocatalytic reactions utilized for information processing ("biocomputing").
Extensive ongoing research in biocomputing, mimicking binary logic gates has been motivated by potential applications in biotechnology. Furthermore, novel sensor concepts have been contemplated with multiple inputs processed biochemically before the final output is coupled to transducing "smart-material" electrodes and other systems. These applications have warranted consideration of networking of biocomputing gates. First few-gate networks have been realized and studied. In order to achieve scalable, stable network design and functioning, considerations of noise propagation and control have been initiated as a new research direction. Optimization of single enzyme-based gates for avoiding analog noise amplification has been explored, as were certain network-optimization concepts. We survey these developments, as well as offer an outlook for possible future research foci. The latter include design and uses of non-binary network elements, specifically, filters, as well as other developments motivated by potential novel sensor and biotechnology applications.
23
Feb '11
Michael Stopa  -  Wednesday, February 23, 2011
ABSTRACT: Photosynthesis starts when a photon is captured by a photosynthetic reaction center containing a chlorophyll molecule. The photon is converted into an excited state of the molecule, a so-called "exciton." In order for the plant to convert that energy into ATP, the energy must be transferred between molecules via a process called Förster resonant energy transfer (FRET). The same process is employed in the design of photovoltaic materials as well as various exotic kinds of excitonic circuits and is even contemplated as a mechanism for implementing quantum computation. The details of how the energy moves in FRET is both an important problem in understanding biological systems and a crucial issue in engineering efficient solar collectors. One of the ways that scientists have studied this problem is in simulations of the electronic structure of molecules and "artificial molecules" known as nanoparticles. The sophistication of these calculations continues to grow as increasingly powerful computer platforms and algorithms become available. In this talk I will describe the calculation of FRET as an important paradigm in electronic structure calculations and show how future developments might solve previously poorly understood problems, such as how quantum mechanics enters into the photosynthetic process in real plants.
28
Feb '11
Bart Kahr  -  Monday, February 28, 2011
Chiroptics of Organized Media
New York University
7
Mar '11
Amnon Moalem  -  Monday, March 7, 2011
14
Mar '11
Warner Miller  -  Monday, March 14, 2011
General Relativity - One Block at a Time
Florida Atlantic University
ABSTRACT: There has been considerable interest in curvature, diffusive curvature flows and general relativity on discrete geometries. This has been applied to broad problems from complex networks to solve the greedy routing problem to Regge calculus to solve Einstein's field equations. Hamilton 's Ricci Flow has garnered considerable interest in its application to help prove the Poincare conjecture by Perelman. We describe here our progress in formulating discrete Ricci flow (DRF) on a simplicial geometry of arbitrary dimension, D. In so doing we provide an explicit and geometric construction of the Riemann tensor, Ricci tensor and the scalar curvature. We will then discuss the discrete formulation of Einstein's geometric theory of gravitation known as Regge calculus.
21
Mar '11
Hyungsik Lim  -  Monday, March 21, 2011
28
Mar '11
Tom Ferbel  -  Monday, March 28, 2011
Whither Particle Physics?
Universities of Rochester and Maryland
ABSTRACT: The next frontier in particle physics is the Large Hadron Collider (LHC), which, having partly recovered from an "incident" two years ago, is restarting now, following a brief preliminary run in 2010 at the European Laboratory for Nuclear and Particle Research (CERN), outside of Geneva, Switzerland. There, two beams of ~ 4 TeV protons (where 1 TeV=1000 GeV, or ~1000 proton masses) will be made to collide head-on, and thereby provide data that will help clarify current puzzles and inadequacies in our conceptual formulation of the nature of the fundamental particles and their interactions. The LHC will respond to specific issues raised by the apparent limitations in the logic of the "standard model (SM)," which is the current, remarkably successful theory of all particle interactions. The development of the SM is arguably the most significant achievement of elementary-particle physics! Its framework accommodates all observed phenomena within a "gauge" quantum-field theory encompassing electroweak (E&M and Weak) and strong (color – QCD) interactions.  Despite that it agrees with all observations, the SM is flawed in that it has many free parameters. But even more telling is that it becomes internally inconsistent beyond TeV energies. The LHC is expected to resolve this scientific conundrum through discovery of new kinds of particles or interactions at this "Terascale." I will describe the nature of the currently disappearing energy frontier at the 1 TeV Tevatron Collider at Fermilab, outside of Chicago, and our hopes for the mightier LHC.
4
Apr '11
Theo Nieuwenhuizen  -  Monday, April 4, 2011
6
Apr '11
Imad Agha  -  Wednesday, April 6, 2011
ABSTRACT: We present experimental studies on the generation of pulsed and continuous-wave squeezed vacuum via nonlinear rotation of the polarization ellipse in a (87)Rb vapor. Squeezing is observed for a wide range of input powers and pump detunings on the D1 line, while only excess noise is present on the D2 line. The maximum continuous-wave squeezing observed is -1.4 +/- 0.1 dB (-2.0 dB corrected for losses). We measure -1.1 dB squeezing at the resonance frequency of the (85)Rb F = 3 --> F' transition, which may allow the storage of squeezed light generated by (87)Rb in a (85)Rb quantum memory. Using a pulsed pump, pulsed squeezed light with -1 dB of squeezing for 200 ns pulse widths is observed at 1 MHz repetition rate.
11
Apr '11
9
May '11
David Schmeltzer  -  Monday, May 9, 2011
19
Sep '11
Ying-Chih Chen  -  Monday, September 19, 2011
ABSTRACT: Convergence of light toward a desired location in optically diffusive and aberrative media is the most important challenge in optical methods of biomedical imaging, where inhomogeneous media with some degree of opacity are generally present. I will review various approaches towards this goal. The techniques include optical phase conjugation, measuring the transmission matrix of forward and back scattered light, and microscopic wavefront adjustments. I will show examples of applying the new understanding and techniques to control spatial coherence in multimode fibers and laser arrays.
5
Oct '11
Guillaume Bal  -  Wednesday, October 5, 2011
ABSTRACT: Imaging in highly heterogeneous media is a notoriously difficult problem because of the presence of unknown clutter. It is often useful to construct functionals of the data that are as independent of the unknown clutter as possible. Field-field correlations are such functionals, which can often be modeled as solutions to kinetic equations. This talk will review basic aspects of such functionals and present results of reconstructions of inclusions buried in strong clutter.
12
Oct '11
Mahua Biswas  -  Wednesday, October 12, 2011
ABSTRACT: The talk will mainly concentrate on the results of optical and morphological properties of zinc oxide (ZnO) nanostructures and on some recent work on organic polymer based photovoltaic devices. Low dimensional nanostructures of ZnO have potential to improve the efficiency and compactness of electronic and photonic devices including LEDs, optical waveguides and sensors. The growth mechanism and characterization of ZnO nanorod and nanowall systems grown on sapphire and Si substrates using vapour phase transport (VPT) method will be presented. The experimental growth conditions to achieve well-aligned ZnO nanorod and naorod/nanowall morphology are optimized by using different forms of carbon powder as source. For ZnO nanostructures to be effectively utilized in devices, it must be possible to dope these structures effectively and homogeneously. The distribution of In and Al dopants with ZnO nanostructures grown on Si and a-sapphire substrates is investigated using low temperature cathodoluminescence. The photoluminescence (PL) peak seemingly unique to ZnO nanostructure at ~3.367 eV, known as the surface exciton (SX) peak, believed to be due to surface adsorbed species are investigated aimed at elucidation of the nature and origin of the emission and its relationship to the nanostructure morphology. The optical and electronic properties of the active layer (usually a blend of semiconducting polymer and fullerene), contributes to the generation of electron-hole (e-h) pairs (excitons) and their dissociation in an organic photovoltaic cell. To improve the optical and electronic properties of the active layer, dye doping in polymers/fullerene blend and concept of hybrid polymer/inorganic nanorod photovoltaic cells are implemented. Dye molecules with the polymer/fullerene composite are used to enhance absorption at longer wavelengths, which could not be harvested otherwise. In hybrid solar cell concept, ZnO nanorods are used in the active layer to increasing the donor-acceptor interfacial area and creating electron transport pathways toward the negative electrode that possess very high electron mobility.
17
Oct '11
Irving Herman  -  Monday, October 17, 2011
ABSTRACT: New materials with potentially new properties and applications can be formed by linking nanocomponents. The assembly of three-dimensional ordered arrays of CdSe and of Fe2O3 nanoparticles by a microfluidics technique is described, along with the formation of hybrids of CdSe nanoparticles and single-walled carbon nanotubes. Coupling between the nanocomponents is important in understanding the new properties these nanomaterials may possess, as is demonstrated by how FRET coupling affects the Stokes shift in photoluminescence from these hybrids. Such systems are also potentially useful in several applications. Nanoparticles are coupled to achieve improved thermoelectric performance. Improved catalytic activity can be achieved using nanoparticles, as is probed by using Raman scattering.
24
Oct '11
Chushun Tian  -  Monday, October 24, 2011
Anderson localization in open media: challenges and progress
Institute of Advanced Study, Tsinghua University, PRC
31
Oct '11
ABSTRACT: This presentation focuses on charge/energy transfer modeling starting from nanoscale quantum phenomena and continuously broadening to macroscale, where these quantum effects can be observed and utilized. Methods of quantum field theory and a quantum transport equation based on the Keldysh-Feynman diagrammatic technique are employed to describe quantum phenomena in the electron-phonon energy exchange [1] and transport phenomena [2,3]. The sophisticated analytical methods used at the nanoscale may be sewed with the numerical Monte-Carlo simulations at larger scales [4]. This approach is used for investigating the charge/energy transfer in nano-materials and for modeling of superconductor and semiconductor nanodevices. I will discuss the design and optimization of next-generation ultra-sensitive detectors, quantum nanocalorimeters, THz mixers, and IR single-photon counters [5]. I will also consider a quantum dot solar cell and its optimization that leads to enhanced harvesting and very efficient photovoltaic conversion of IR energy [6].
1. Y.-L. Zhong, A. Sergeev et al., Phys. Rev. Lett. 104, 206803 (2010).
2. M. Bell, A. Sergeev, et al., Phys. Rev. Lett. 104, 046805 (2010).
3. A. Sergeev, M. Reizer, and V. Mitin, Phys. Rev. Lett. 106, 139701 (2011); Europhys. Letters 92, 27003 (2010).
4. V. Mitin, A. Sergeev, L-H. Chien, and N. Vagidov, Large-Scale Scientific Computing, Springer, p. 403, 2010.
5. B.S. Karasik, A. Sergeev, and D. Prober, "Nanobolometers for THz photon detection," IEEE Trans. on Terahertz Science & Technology, 1 (Inaugural Issue), 97 (2011).
6. K.A. Sablon, J.W. Little, V. Mitin, A. Sergeev, N. Vagidov, and K. Reinhardt, Nano Letters 11, 2311 (2011).
7
Nov '11
Felix Izrailev  -  Monday, November 7, 2011
Anderson Localization in Bi-layered Structures with Compositional Disorder
Instituto de Fisica, BUAP, Mexico, and Michigan State University
ABSTRACT: The localization length (LL) has been derived for one-dimensional bi-layered structures with random perturbations in the refractive indices for each type of layers. Main attention is paid to the comparison between conventional materials and those consisting of mixed right-hand and left-hand materials. It is shown that the localization length is described by the universal expression for both cases, when the widths of layers of right-hand and left-hand materials are different. In a specific case, when the widths are equal, our analytical approach demonstrates that the inverse LL vanishes in the first order of perturbation theory. We were able to develop the expression for the LL with higher order terms, and explain puzzling numerical results, recently discussed in literature.
14
Nov '11
Hakan Tureci  -  Monday, November 14, 2011
21
Nov '11
Jing Wang  -  Monday, November 21, 2011
5
Dec '11
Parameswaran Nair  -  Monday, December 5, 2011
6
Feb '12
Justin Vazquez-Poritz  -  Monday, February 6, 2012
String theory versus the real world
New York City College of Technology, CUNY
ABSTRACT: Even though string theory is a leading candidate for a theory of everything, it has the rather embarrassing requirement that there are nine dimensions of space. In order for this not to conflict with the fact that we observe only three dimensions of space, six of the dimensions must somehow remain hidden. I will provide a non-technical overview of three different ways of hiding these extra dimensions. This has led to the possibility of unifying all forces within a geometrical framework, new methods for computing quantities in nuclear physics as well as condensed matter systems, and concrete predictions that could potentially falsify certain aspects of string theory.
21
Feb '12
Hyun-Joong Kim  -  Tuesday, February 21, 2012
ABSTRACT: This lecture addresses fundamental concepts of pressure sensitive adhesives (PSA), and developments in industry. Pressure-sensitive-adhesives (PSA) are distinct from general adhesives, as evidenced by phase separation in the curing process and by modes of failure. PSAs are potentially easier to process, can be reusable and easy to remove, and have application in fields such as electronics, semiconductors, transportation, and health. Recent research is directed at eco-friendly, highly functional materials that meet international regulations.
5
Mar '12
ABSTRACT: New solutions for thermal management have been sought recently due to increasing density of dissipated power in modern sub-50 nm electronic devices. Heat transport in nanostructures is affected both by bulk thermal resistances and by thermal coupling across the interfaces between dissimilar materials. The interface thermal resistance, also known as a Kapitza resistance, is in the focus of this talk. Highest intrinsic thermal conductivity of nano-carbons (such as graphene and nanotubes), closest to or even exceeding the diamond, is not helpful enough until one can efficiently connect the nano-carbon to the substrate. We will show that the near-field radiation, or quantum-electrodynamic Kapitza conductance mechanism is the main term in the heat exchange between the polar substrate and graphene or tubes. Such quantum terms may be anticipated to allow a breakthrough in the existing thermal technologies, and, at least, change our understanding of the heat transport at the nanoscale, still largely based on the classical thermal physics.
12
Mar '12
Ethan Schonbrun  -  Monday, March 12, 2012
Optofluidics for High Speed Microscopy
Rowland Institute, Harvard University
ABSTRACT: Flow cytometry has become a benchmark technology due to its ability to individually characterize extremely large collections of particles or cells. Despite its impressive throughput, flow cytometry requires labeled objects and typically looses all spatial information of each cell. Instead of just quantifying scattering and absorption cross-sections, as is done in flow cytometry, it would be highly advantageous to capture full two or three-dimensional images of cells at the same throughput. Imaging, and especially fluorescence and three-dimensional imaging, is extremely challenging at these speeds due to the required short exposure time and fast acquisition rates. In this talk I will address some of the strategies that our lab is using to address these problems, primarily parallelization, fluidic manipulation, and alternative optical contrast mechanisms.
19
Mar '12
Christina Othon   -  Monday, March 19, 2012
ABSTRACT: Biological systems consist of a complex, heterogeneous mixture of proteins, lipids, carbohydrates, water, and a myriad of other small molecules. Structural biologists have long focused on the relationship between protein structure and function in investigating biological processes. Few recognize the essential role the solvent plays in dictating structural transitions and self-assembly. In this talk we discuss two experiments that exploit solvent interactions and organization in order to manipulate protein structure and self-assembly at the molecular level. In the first part of the talk we will discuss fluorination of proteins as a tool to enhance protein stability through alterations in hydration dynamics. In the second part of the talk we will discuss the tools being developed at Wesleyan to investigate lipid phase transitions. Lipid phase stability and clustering are essential to the recognition, insertion, and self-assembly of proteins within the lipid membrane. Using our technique we can resolve these highly dynamic processes to unambiguously identify orientation and dynamic freedom within our membrane model with the highest available temporal resolution, and without the restriction imposed by a supporting substrate.
26
Mar '12
Philip Kim  -  Monday, March 26, 2012
ABSTRACT: The two most important achievements in physics in the 20th century were the discoveries of the theory of relativity and quantum physics. In 1928, Paul Dirac synthesized these two theories and wrote the Dirac equation to describe particles moving close to the speed of light in a quantum mechanical way, and thus initiated the beginning of relativistic quantum mechanics. Graphene, a single atomic layer of graphite discovered only a few years ago, has been provided physicists opportunities to explore an interesting analogy to relativistic quantum mechanics. The unique electronic structure of graphene yields an energy and momentum relation mimicking that of relativistic quantum particles, providing opportunities to explore exotic and exciting science and potential technological applications based on the flat carbon form. As a pure, flawless, single-atom-thick crystal, graphene conducts electricity faster at room temperature than any other substance. While engineers envision a range of products made of graphene, such as ultrahigh-speed transistors and flat panel display, physicists are finding the material enables them to test a theory of exotic phenomena previously thought to be observable only in black holes and high-energy particle accelerators. In this presentation I will discuss the brief history of graphene research and their implications in science and technology.
2
Apr '12
Francis Starr  -  Monday, April 2, 2012
16
Apr '12
Fred Cadieu  -  Monday, April 16, 2012
ABSTRACT: When two groups of physicists started to use bright supernova explosions to extend distance measurements to far away objects, they came to the very surprising conclusion that these supernovae were fainter than expected. The only explanation seemed to be that some time ago the rate of expansion of the universe had started to accelerate! This interpretation is based on a confluence of results from many recent Nobel prizes in physics which has led to the field of high precision cosmology. Certain aspects of Type 1A supernova explosions that have allowed these to act as standard candles for extending distance measurements billions of years into the past will be discussed. The most recent results, which revolutionized our current understanding of the universe, will be shown to be consistent with the Big Bang Model.
30
Apr '12
Stefan Bathe  -  Monday, April 30, 2012
The Hottest Matter on Earth
Baruch College of CUNY
ABSTRACT: A few microseconds after the Big Bang, the Universe was too hot for quarks and gluons to be confined into hadrons. But then, what is the nature of this primordial matter? At the Relativistic Heavy Ion Collider (RHIC), we can recreate the conditions of the early Universe and study this matter in the laboratory. I will review the key findings of the experiments and discuss recent developments of the field.
7
May '12
Bidisha Roy   -  Monday, May 7, 2012
4
Sep '12
Yisa Rumala  -  Tuesday, September 4, 2012
ABSTRACT: A common way of imprinting orbital angular momentum on light is by using an ideal spiral phase plate. This is a device consisting of a piece of transparent material with an azimuthally varying thickness. When light goes through the device, it acquires an azimuthally varying phase containing orbital angular momentum. In this talk, I will describe a spiral phase plate which has non-zero reflectivity on both surfaces, such that the rays of light makes multiple reflections with the azimuthally varying surface before exiting the device. In this case, the exiting beam will contain a coherent superposition of orbital angular momentum modes with the appearance of an optical intensity pattern that varies as a function of angle on the output plane of the device. When the laser frequency is changed, the optical intensity pattern is observed to rotate. This is the first time that this effect has been quantified. The work extends the conventional Fabry-Perot etalon to a new geometry, namely the spiral phase plate etalon; and it is expected to have broad applications in optical frequency metrology, quantum optics, and atom optics.
10
Sep '12
Nicolas Giovambattista  -  Monday, September 10, 2012
ABSTRACT: Most liquids can form a single glass or amorphous state when cooled fast enough, so crystallization is avoided. However, there are a few substances that are relevant to scientific and technological applications that can exist in at least two different amorphous states, a property known as polyamorphism. Examples include silicon, silica, and in particular, water. In the case of water, experiments show the existence of a low-density (LDA) and high-density (HDA) amorphous ice that are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation connects to a first-order liquid-liquid phase transition (LLPT) above the glass transition temperature Tg. However, direct experimental evidence of the LLPT is challenging to obtain, since the LLPT occurs at conditions where water rapidly crystallizes. In this work, we (i) discuss the general phenomenology of polyamorphism in water and its implications, and (ii) explore the effects of a LLPT on the pressure dependence of Tg(P) for LDA and HDA. Our study is based on computer simulations of two water models -- one with a LLPT (ST2 model), and one without (SPC/E model). In the absence of a LLPT, Tg(P) for all glasses nearly coincide. Instead, when there is a LLPT, different glasses exhibit dramatically different Tg(P) loci which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario that includes a LLPT (ST2 model) and hence, our results support the view that a LLCP may exist for the case of water.
24
Sep '12
Mikhail Shneider  -  Monday, September 24, 2012
Molecular ensembles in non-resonant optical lattices
Applied Physics Group, Department of Mechanical and Aerospace Engineering
ABSTRACT: In this talk recent theoretical and experimental results on the interaction of optical lattices with neutral gases will be reviewed. Small gas density perturbations produced by the electrostrictive effects of laser beams (when the optical potential well depth << kT) can be used for powerful nonintrusive diagnostics based on coherent Rayleigh and Rayleigh-Brillouin scattering. Effects such as bulk drift can be induced in a gas by a periodic optical traveling wave (lattice), even when the mean kinetic energy is much greater that the maximum optical potential provided by the field. With increasing laser beam intensities, the optical potential can trap a large fraction of the gas. In this case, acceleration or deceleration of the gas is possible. Gas particles cannot be trapped in the highly collisional regime. Analysis of the trapped and untrapped motion of particles demonstrates that atoms and molecules can be accelerated from room temperature to velocities in the 10 to 100 km/s range over distances of 100s of microns. Recently, such experiment was successfully performed by Dr. Peter Barker's group in Great Britain. The effects of coupling of non-resonant laser radiation to a gas will be discussed. In all cases when a lattice induces a periodic modulation of the gas density, strong Bragg diffraction of light can occur. It can potentially limit the achievable intensities inside the optical lattice limiting the ability to manipulate the gas. The self-consistent evolution of the input laser beams via the light-induced perturbation of the index of refraction can be determined by the solution of the wave equation in the interference region together with the Boltzmann kinetic equation for gas.
15
Oct '12
Alan Calder  -  Monday, October 15, 2012
ABSTRACT: Supernovae are spectacular explosions that signal the violent death of a star. Supernovae produce and disseminate heavy elements, trigger star formation, and in some cases may be used as distance indicators for cosmological studies. These fascinating events encompass a broad range of physics, and realistically modeling these requires the largest supercomputers. I will give an overview of supernovae and our theoretical understanding of these events and present results from our research into type Ia (thermonuclear) supernovae. Our models and statistical framework allow the systematic study of how properties of the host galaxy can influence the brightness of an event. I will present the results from ensembles of simulations addressing the influence of age and metallicity on the brightness of an event and compare our results to observed trends in brightness with age and color of the host galaxy.
22
Oct '12
Jon Swaim  -  Monday, October 22, 2012
Plasmonics in the Whispering Gallery
University of Queensland, Australia
ABSTRACT: Whispering gallery mode (WGM) resonators are optical cavities with extremely high quality factors (up to 10^8) in air and water. In this talk I will present results on chip-based microtoroids as nanoparticle sensors and discuss their feasibility as single molecule detectors. I will discuss a variety of approaches for enhancing the sensitivity in the context of biosensing. In particular, we show through numerical modeling that coupling of plasmonic nanoparticles to WGM fields leads to large enhancements in sensitivity which may enable single molecule detection under practical experimental conditions. In addition, we observe experimentally that coupling of plasmonic nanoparticles (39x10 nm gold nanorods) leads to interesting changes in the optical spectra which are currently not fully understood, but related to theoretical predictions in the literature. These effects have the potential for enhanced measurement in sensing both the position and size of nanoscale objects. Lastly, I will present results on the first ever optomechanical magnetometer, with current sensitivity of 400 pT/root Hz; and experiments towards achieving the quantum ground state of vibrational modes in microtoroids, an enabling step towards quantum optomechanics.
5
Nov '12
Chushun Tian  -  Monday, November 5, 2012
Driven systems: from classical chaos to unusual quantum matter
Institute of Advanced Studies, Tsinghua University
26
Nov '12
Micha Tomkiewicz   -  Monday, November 26, 2012
Democratization of Climate Change
Brooklyn College of CUNY
ABSTRACT: I will try to outline four major challenges to the democratization of the decision making process that in my view are needed to address the challenges that anthropogenic changes in the chemistry of the atmosphere will pose: Climate Change and the Nature of Science - We are now part of the physical world on planet earth. When we try to investigate global phenomena such as climate change we include us in the system that we investigate. In medical or legal terms this process is called self-diagnosis or self-defense. A common saying is that a lawyer that serves as his own legal adviser got a fool for a client. The same holds true for a doctor that tries to treat himself in a serious medical issue. Doctors and lawyers have the options to hire somebody else. The global human population doesn't. We didn't yet identify an exoplanet that can help. "Hate of Science" - Most of us hate science and students that takes my courses that are identified as science courses, tell me with great pride that they "despise" math We are not prophets - The Popperian scientific method is based on refutability. We develop hypothesis and theories based on everything that we know and we should be able to test the theory based on predictions for observations that we didn't yet make. If the tests fail - we change the theory. This amounts to prediction of future results. Since we are part of the system - failure might mean closing the window that allows us to survive. NIMBY (Not In My Backyard) - Climate Change is a global, collective, phenomena that all of us contribute to and all of us, sooner or later are being affected by. The common denominator in all of these challenges is that in my view all of them can be addressed through the educational system. The instruments that we are developing include a "popular" blog (climatechangefork), a book that was just published titled "Climate Change: The Fork at the End of Now" that was written to serve as a textbook for the general public; development of a multiplayer electronic learning system, built on social/scientific simulations and fed by relevant and timely databases that require students to make choices and examine the consequences of these choices; and a documentary film that documents energy transition in the Sunderban region of India from hunter-gatherer to electrified modern existence.
3
Dec '12
Morton Denn  -  Monday, December 3, 2012
Paths to Macroscopic Constitutive Equations
Levich Institute, City College, CUNY
ABSTRACT: Complex fluids, including polymer melts and solutions, liquid crystals, colloidal and non-colloidal suspensions, etc., are routinely used in consumer and industrial applications and are present in many natural systems. Experimental rheology gives insight into the behavior of such systems in elementary flows and may point to underlying physical phenomena, but the ability to carry out computations in the complex geometries that are normally of interest requires continuum descriptions that can be integrated into conservation equations. Such constitutive equations may arise from empirical considerations, from microstructural analysis, or from fundamental principles of continuum mechanics. The history of the development of constitutive equations for flexible polymeric systems over six decades involves all three approaches, and there has been a synthesis over time that enables meaningful process calculations, although much remains to be done. Other areas are less developed. Continuum theories for suspensions, in particular, remain at a relatively primitive stage that is reminiscent of the situation for polymers many decades in the past, but it is likely that progress will be more rapid because of the ability to integrate ideas from the polymer community and elsewhere. In this talk we will look first at the development of macroscopic constitutive equations for flexible polymers and then consider the state of development and outstanding issues for suspensions.
10
Dec '12
Frederick Walter   -  Monday, December 10, 2012
ABSTRACT: The galactic novae are thermonuclear explosions in a degenerate hydrogen layer on the surfaces of white dwarf stars. This is inferred from energetics and plausibility arguments, but the lack of uniformity of the novae shows that they are much more complex, and interesting. Novae are highly dynamic phenomena, involving brightenings by up 20 magnitudes, and velocities of over 5000 km/s in extreme cases. Eight years ago we initiated a project to generate a more-or-less uniform set of spectroscopy and photometry of novae accessible to the SMARTS facilities at the Cerro Tololo InterAmerican Obervatory. The atlas now contains observations of over 60 novae, some observed for as long as 8 years past their eruption. Following a general description of the nova phenomenon, I shall turn to two topics that I am currently engaged in. The first is an attempt to explain the peculiar line profiles of the He-N (or recurrent) novae. These do not resemble the optically thick shells of the Fe II (or classical) novae, but can be modeled as optically-thin accretion disks. If so, this will require a change in our understanding of the inner environs of the novae. The second is an examination of the N III Bowen fluorescence lines, and their relation the He II 4686 line. This mechanism is understood in the static case, but the novae are highly dynamic. The lightcurves of the N III and He II lines and the supersoft X-ray flux suggest an interpretation as a temperature gauge.
6
Feb '13
Humeyra Caglayan  -  Wednesday, February 6, 2013
ABSTRACT: Bringing circuit functionalities into the optical domain requires the introduction of new conceptual paradigms and experimental methods, and would represent an important advance in nanoelectronics technology. In this seminar, I will introduce the lumped circuit elements in the near infrared regime by making use of plasmonic materials and simple geometries with subwavelength cross-sectional dimensions. The control of the functionality of these optical nanocircuits, completely consistent and analogous with the notion of radio-frequency circuits, and can be done by changing the impedances of the circuit elements. Such nanocircuits' elements function as building blocks for future plasmonic devices.

I will also present a novel structure that effectively behaves as an n=0 metastructure in the visible and near-infrared spectral range. This metal/dielectric optical waveguide structure operating at the cutoff of its TE mode behaving effectively as an Epsilon-Near-Zero (ENZ) metamaterial, exhibiting uniform phase distribution and essentially uniform amplitude, which enables opportunities for better control and enhancement of light propagation in waveguides, as well as development of nano-photonic devices. Finally, I will discuss the effect of the ENZ medium on the control of degree of coherence by comparing the field radiated by sources with varying degrees of randomness in a conventional medium to that in an ENZ medium.
11
Feb '13
Alexander Khanikaev  -  Monday, February 11, 2013
ABSTRACT: Metamaterials, the artificial electromagnetic media with properties beyond those found in natural materials, have been a subject of intensive studies for over a decade and as the field evolves, new avenues for their applications are emerging. In this talk, I will focus on the possible applications of Fano resonant metamaterials stemming from their ability of enhancing light-matter interaction due to strong confinement of electromagnetic field by subradiant modes. I will show how metamaterials can be endowed with new unique functionalities by combining them with other complex media, such as magnetic materials, biomolecules, and graphene. In particular, the nonreciprocity can be engineered and ultra-thin optical diodes can be created by combining metamaterials with magneto-optical materials. It will also be shown how the interaction of high-quality mid-IR modes of Fano-resonant metamaterials with the vibrational modes of biomolecules facilitates the detection of protein monolayers and their characterization to an unprecedented degree. Finally, I will present our recent theoretical and experimental results on light scattering in metamaterial/graphene heterostructures and propose how such hybrid photonic-electronic systems can be used to build tunable photonic devices.
13
Feb '13
Pai-Yen Chen  -  Wednesday, February 13, 2013
ABSTRACT: Plasmonics has opened the possibility to strongly enhance light-matter interaction at the nanoscale, opening new opportunities to manipulate and confine light at dimensions unthinkable only a few years ago. Plasmonic nanostructures can enhance weak optical responses and nonlinear optical effects, and can serve as information carriers for the next-generation of heavily integrated nanophotonic systems. Optical metamaterials formed by large arrays of subwavelength plasmonic nanostructures can open even more exciting scenarios, by exploiting the collective coupling interaction among many nanoinclusions to realize bulk optical properties that cannot be found in nature, such as a negative optical index of refraction. In my talk,I will describe our recent research efforts on optical nanoantenna arrays and optical metamaterials, studying their exciting physics and their practical use and application in highly-efficient thermoelectric and thermophotovoltaic solar cells, photothermal therapy and nanoscale nonlinear optical processes, including wave mixing, harmonic generation, phase conjugation and optical bistable effects. In addition, I will discuss how the extreme local field enhancement around nanoantennas can benefit ultrafast photon-assisted field emission processes, optical heterodyne terahertz (THz) generation and multiple-photon photoemission from nano-emitters, enabling compact, low-cost, low-power THz generation, free-electron lasers and X-ray sources. I will also discuss how the anti-phase polarization of a plasmonic coating may be used to realize invisibility and transparency effects. As an extreme case of light manipulation at the "atomic" scale, I will discuss the collective oscillation of massless Dirac fermions inside grapheme monolayers, in which surface plasmon polaritons may be controlled by the graphene's tunable surface conductivity using electrostatic gating. I will conclude my talk discussing active and tunable THz nanodevices and nanocircuits, and graphene-based THz metamaterials.
20
Feb '13
Boris Shapiro  -  Wednesday, February 20, 2013
Fluctuating thermal electromagnetic fields
Technion, Israel Institute of Technology
ABSTRACT: A hot body radiates an electromagnetic flux according to Kirchhoff's law. However, close to the body surface there are strong fluctuating fields which do not contribute to the electromagnetic flux. These fields are evanescent and decay exponentially away from the surface. Some phenomena, related to those fields, will be discussed and the effect of stationary currents on the electromagnetic field fluctuations will be pointed out.
4
Mar '13
Hanwei Gao  -  Monday, March 4, 2013
ABSTRACT: Surface plasmons have been investigated intensively because of their unique properties for optical confinement and light manipulation on subwavelength scales. Research on both fundamentals and applications of surface plasmons are advanced by rapid development of nanoscale synthesis and fabrication techniques. By defining nanostructures in metals, these traditional electrical conductors are functionalized with plasmonic properties, which have led to exotic phenomena such as negative light refraction, surface enhanced Raman scattering, and subwavelength focusing. In this talk, I will discuss how surface plasmons in periodically patterned metals can be identified, characterized, and tuned using near-field and far-field optical methods. These periodic nanostructures, also known as plasmonic crystals, provide versatile platforms for discovering and screening new plasmonic materials. Rationally designed plasmonic crystals have also shown promises for applications from biochemical sensing to solar energy harvesting.
6
Mar '13
Alessandro Salandrino  -  Wednesday, March 6, 2013
ABSTRACT: Diffraction effects are ubiquitous in all phenomena involving the propagation of waves. As an example, in optics and photonics the so-called "diffraction limit" imposes a fundamental limit on the resolution that an optical instrument can achieve, or on the confinement that a beam can maintain during propagation. In this talk I will present novel strategies to manage or to completely counteract the effects of diffraction. The far reaching consequences of the proposed schemes include the possibility of achieving far-field sub-diffraction imaging, evanescent wave recovery and diffraction-free, self-healing plasmonic propagation.
11
Mar '13
Hebin Li  -  Monday, March 11, 2013
Optical Multi-dimensional Fourier Transform Spectroscopy
JILA, University of Colorado and National Institute of Standards and Technology
ABSTRACT: The concept of multi-dimensional Fourier transform spectroscopy originated in nuclear magnetic resonance (NMR) where it revolutionized NMR studies of molecular structure and dynamics and led to the Nobel Prize in Chemistry in 1991. In the past decade, the same concept has been implemented in the optical region with femtosecond lasers. In the experiment, the nonlinear response of a sample to multiple laser pulses is measured as a function of time delays. A multi-dimensional spectrum is constructed by taking a multi-dimensional Fourier transform of the signal with respect to multiple time delays.
In this presentation, I will introduce optical multi-dimensional Fourier transform spectroscopy and its applications to study a potassium (K) vapor and semiconductor nanostructures. The K vapor provides a simple test model to validate the method, while the obtained 2D spectra reveal the surprising collective resonance due to the dipole-dipole interaction in a dilute gas. By extending the technique into a third dimension, 3D spectra can unravel different pathways in a quantum process and provide complete and unambiguous information to construct the full Hamiltonian of the system. Besides atomic/molecular systems, optical multi-dimensional Fourier-transform spectroscopy is also a powerful tool for studying many-body dynamics and coupling in solid-state systems such as semiconductor nanostructures. I will present several applications in semiconductor quantum wells and self-assembled quantum dots, where unique information about the systems can be obtained from 2D spectra.
18
Mar '13
Ryan Thomas Glasser  -  Monday, March 18, 2013
Fast Light and Quantum Entanglement
National Institute of Standards and Technology
ABSTRACT: Quantum states of light have been shown to provide improvements in a variety of systems, resulting in provably secure communication, sub-shot noise interferometry, and computation schemes that scale better with resources than when using classical means. A key aspect of these entangled and squeezed states of light is that they exhibit correlations that are stronger than allowed classically. Due to the important role entanglement plays in the field of quantum optics, numerous investigations into its fundamental behavior have taken place. For example, how entanglement evolves when propagating through a slow light medium, in which the group velocity of light is less than the speed of light in vacuum, c, have been conducted in the past. We seek to investigate how quantum correlations and entanglement behave when propagating through a medium exhibiting anomalous dispersion. In such a medium, optical pulses may propagate with group velocities that are larger than c, or even negative. In this talk I will show that by using a nondegenerate four-wave mixing (4WM) process in warm rubidium vapor, which may be used to generate squeezed and entangled states of light, it is possible to generate pulses with record negative group velocities. Additionally, I will discuss recent results involving the combination of fast light and quantum entanglement. Finally, I will present ongoing research involving secure quantum key distribution and phase-sensitive image amplification, and conclude with a discussion of future research directions involving the versatile 4WM system.
8
Apr '13
Ravindra Bhatt  -  Monday, April 8, 2013
29
Apr '13
David Grier  -  Monday, April 29, 2013
The Guiding Light: Holographic Control over the Microscopic World
Department of Physics and Center for Soft Matter Research, New York University
ABSTRACT: This talk focuses on the statistical mechanics of micrometer colloidal particles moving through landscapes of force and torque that are created with computer-generated holograms. These optical force fields can take the form of discrete optical tweezers that can trap and hold microscopic objects in three dimensions. They also can be far more exotic, and include the first experimental implementation of a knotted force field, and the first successful demonstration of a true tractor beam. In addition to the conservative forces that create traps, holographically structured light fields also exert non-conservative forces whose intriguing ramifications we observe with holographic video microscopy. These observations reveal a previously unrecognized category of stochastic heat engines.
23
Sep '13
Eric Cramer  -  Monday, September 23, 2013
ABSTRACT: Although lightning is one of the most commonly known and destructive natural phenomena on Earth, it remains poorly understood in terms of the most basic physics. Questions such as how it is created inside thunderstorms and how it manages to travel many tens of kilometers are still being worked out today. Benjamin Franklin is considered to be the pioneer of this research field, propelled by his famous kite experiment that showed lightning to be an electrical discharge. Since that time, lightning experiments have been relatively difficult to achieve due to its seemingly random occurrence, unpredictability and short duration. However, over the last decade, the research groups at Florida Institute of Technology and the University of Florida have made detailed measurements of the lightning discharge using a rocket triggering technique at the International Center for Lightning Research and Testing (ICLRT). A consequence of this study has been the discovery that lightning emits x-rays and gamma-rays as it travels through the atmosphere and down to Earth's surface. In 1994, NASA satellite data from the Compton Gamma-Ray Observatory, originally designed to measure gamma-ray bursts from distant galaxies, discovered intense glows of radiation being emitted from the Earth. These discharges were so bright (up to 40 MeV), that they saturated all the high energy detectors onboard the spacecraft. After many similar events were observed, these phenomena, known as Terrestrial Gamma-Ray Flashes (TGFs), were shown to originate from within the thunderstorm region. Most recently, the potential radiation doses that airline passengers would experience inside the core of a TGF have been calculated. It has also been determined, with remote radio measurements and theoretical modeling, that a new type of electrical discharge, called "dark lightning", is responsible for these high energy events. However, its relationship to a normal lightning discharge still remains a mystery. Many other exotic phenomena have also been observed as a result of thunderstorms including halos, elves, sprites and blue jets. The fact that these lightning related events can affect the upper atmosphere and lower ionosphere has reshaped the scientific field to the study of high energy atmospheric physics. The research done on lightning has thus fused many areas of physics including plasma physics, atmospheric physics, and quantum electrodynamics. The rapidly expanding field has opened many opportunities for both theoretical and experimental studies. Mathematical modeling, including Monte Carlo simulations, has given us a better understanding about the nature of particle acceleration inside the high field regions of thunderstorms. Likewise, instrumentation including photomultiplier tubes, high speed video cameras, and electric field antennas, has helped us gain a better insight into the lightning discharge near the ground. In this talk, we review the history of lightning research, show many of its recent developments, and lay out the questions that are being addressed today by many physicists, meteorologists and engineers around the world. We also hope to expand the importance of lightning safety and the awareness of exciting research opportunities for many young scientists.
30
Sep '13
15
Oct '13
Seppe Kuehn  -  Tuesday, October 15, 2013
21
Oct '13
Emil Prodan  -  Monday, October 21, 2013
ABSTRACT: Topological Insulators and Superconductors are novel materials with non-trivial energy-band topology. This non-triviallity has important physical consequences, such as the emergence of chiral edge or surface bands at the boundary of the samples, or quantized electric and magneto-electric responses. Depending on their generic symmetries, the topological materials fall in several distinct classes. An ongoing effort is understanding what are the physical properties that remain robust in the presence of strong disorder. Some fundamental questions, which apply to all these distinct classes of topological materials, are: Do the edge and surface modes localize? Are there extended states in the bulk (as in the IQHE)? Does the Magneto-Electric response remain quantized in the presence of strong disorder? In this talk, I will give a brief historical account of the field and bring up-front some of the present challenges and new research directions. In the second part I will introduce a non-commutative geometry program for topological insulators, which enabled us to make analytical and computational progress in the field of strongly disordered topological materials.
28
Oct '13
Dmitri Vainchtein  -  Monday, October 28, 2013
ABSTRACT: In my talk I discuss several aspects of transport phenomena in the near-integrable multiscale dynamical system. Multi-scale systems naturally arise when a small perturbation is added to an integrable base (or unperturbed) subsystem. Not only are such systems common in various applications, this is the only class of dynamical systems that generically affords a quantitative analytical treatment. Direct brute-force numerical simulation of such systems are possible, but usually are very challenging precisely due to a big separation of time scales. Approximate analytical tools represent an important alternative for studying such systems. An approach that greatly simplifies the description of the mixing dynamics in multi-scale systems is based on the method of averaging: in order to study long-time dynamics, the equations of motion for phase points are averaged over the fast time scale(s). In the present talk I illustrate the glory and the fall of the method of averaging by considering two examples: one from microfluidics and one from plasma physics. In the first part of the talk I consider mixing via resonances-induced chaotic advection in microdroplets. I show that proper characterization of the mixing quality requires introduction of two different metrics. The first metric determines the relative volumes of the domain of chaotic streamlines and the domain of regular streamlines. The second metric describes the time for homogenization inside the chaotic domain. In the second part of my talk, I describe the resonant interaction between monochromatic electromagnetic waves and magnetized electrons in configurations with magnetic field reversals (e.g. in the earth magnetotail). I discuss in two resonant phenomena occurring during slow passages of a particle through a resonance: capture into resonance and scattering on resonance. These processes result in destruction of adiabatic invariant, chaotization and almost free acceleration of particles. We calculate the characteristic times of mixing due to resonant effects and the rates of the acceleration.
11
Nov '13
ABSTRACT: In this seminar, we will focus on two aspects of our work that look at materials which have been studied for quite some time, but try to utilize them in new and interesting ways. In the first part, we will look at metals, specifically Au and Ag. It turns out that metals, like semiconductors, can be quantized for diameters <2 nm. At such sizes in fact, even relatively efficient quantum yields of emission have been demonstrated. Here, we look at thin films of metal nanoclusters (MNCs), and demonstrate a thin film LED with either Au or Ag MNCs as the emitting element. In both cases, the electroluminescence peak of the LED corresponds with the photoluminescence of the MNCs in solution. In the second part, we will focus on our recent efforts to template the growth of organic semiconductors. Through proper control of crystal phase, molecular orientation, and grain size (from nm to μm), we are able to realize higher solar cell performance from "classical" materials than otherwise possible.
18
Nov '13
Vadim Oganesyan  -  Monday, November 18, 2013
Many-body localization
College of Staten Island
25
Nov '13
ABSTRACT: The concepts of open and closed channels are useful to understand transport properties in disordered open media. We will review the physics of open channels and introduce a new random matrix ensemble that allows to predict the values of transmission or reflection achievable with wavefront shaping techniques in lossless or weakly absorbing media. This ensemble is parameterized by an effective fraction of controlled channels that we calculate microscopically. Its expression depends on the geometry (waveguide or slab), the illumination protocol (numerical aperture, size and shape of the illumination profile), and the long-range mesoscopic correlations of the medium. We will report measurements of the transmission eigenvalue density and of the total transmission in agreement with theoretical predictions. Finally, we will show that the same theoretical formalism can be used to predict the classical information capacity of a disordered medium as well as the effect of the disorder on the entanglement properties of a given input state of light.
2
Dec '13
3
Feb '14
ABSTRACT: Living objects at the nanoscale can be viewed as molecular complexes, whose dynamics is often controlled by the transfer of single charges or single-photon absorption events. In many senses, it is similar to the principles of operation of semiconductor nanostructures and elements of molecular electronics. Correspondingly, the methods of condensed matter and statistical physics can be applied.
In this talk, I address proton-pumping complexes and proton-driven nanomotor of the mitochondria membranes. These systems convert the energy obtained from the food to the proton gradient across the membrane, to the mechanical rotation of the nanomotor, and, finally, to the energy of chemical compounds. We propose simple physical models for these complexes which not only allow the quantitative description but can inspire the implementations in nanoelectronics as well.
In the end of the talk, I discuss some details of electron transfer calculations bridging the Marcus theory and equations of motion, two methods widely used in chemistry and physics, respectively. We demonstrate that as a manifestation of the Goldilocks principle, the optimal transfer is governed by a single parameter which is equal to just the inverse square root of two.
10
Feb '14
Rafael Ben-Michael  -  Monday, February 10, 2014
ABSTRACT: The Discrete Amplification Photon Detection technology enables a unique photodetector, in which a combination of an avalanche and negative-feedback mechanisms produces ultra-sensitive, very high gain, low noise, very small pixel size photodetectors and photodetector arrays.  The discrete amplification physical mechanism is not dependent on the ratio of electrons and holes ionization coefficients, thus it can be implemented in several compound semiconductor material systems, such as silicon, GaAs/AlGaAs, and InGaAs/InGaAsP/InP.  This talk describes the operation principle of the technology, the advantages and tradeoffs, as well as how this technology compares to, and differs from, other competing high sensitivity approaches.  As this technology can detect single photons, single-photon detection and characterization will be described, as well as other low-light level threshold detection methodologies used to characterize the Discrete Amplification photodetectors.  Record setting sensitivity results at room temperature detection using 1.5 micron wavelength-sensitive detectors will be presented.  In addition, the development status of the technology, development plans and challenges for the two main applications, night vision and ranging, will be described.
14
Feb '14
Hiroyuki Takagi  -  Friday, February 14, 2014
Holographic Display
Toyohashi University of Technology, Japan
PDFDownload PDF talk time4:00 pm
NOTES: Event starts at 4:00 PM on Friday
24
Feb '14
Vadim Oganesyan  -  Monday, February 24, 2014
3
Mar '14
ABSTRACT: Recent progress in femtosecond electronic spectroscopy brought renewed interest in the transfer of electronic excitation energies in large molecular complexes.  In particular, there have been speculations that the energy transfer in some photosynthetic light harvesting complexes may involve wave-like coherent quantum dynamics motion rather than the rate behavior.  However, to what extent the quantum coherence is detrimental to efficient and robust energy transfer has remained a controversial issue.  Advanced level of theories and development of reliable quantum mechanical models are crucial for quantitative resolution of such issue.  This talk will present a range of theories developed recently, which can address nonequilibrium effects, quantum coherence, and soft nature of molecular environments for a fairly general class of systems. The talk will also discuss exciton-bath modeling of photosynthetic light harvesting complexes and quantum dynamical calculation of energy transfer dynamics.  These results suggest that quantum coherence can play a subtle but significant role in minimizing the negative effects of thermal fluctuations and disorder in order to create both efficient and robust energy transfer dynamics mechanism. 
10
Mar '14
Pouyan Ghaemi  -  Monday, March 10, 2014
ABSTRACT: Many of the topological insulators, in their naturally available form are not insulating in the bulk. It has been shown that some of these metallic compounds, become superconductor at low enough temperature and the nature of their superconducting phase is still widely debated. In this talk I show that even the s-wave superconducting phase of doped topological insulators, at low doping, is different from ordinary s-wave superconductors and goes through a topological phase transition to an ordinary s-wave state by increasing the doping. I show that the critical doping is determined using the SU(2) Berry phase on the fermi surface of doped topological insulator and can be modified by different tunable features of the material. At the end I present the results of a recent experiment on the Josephson junctions made of thin films of Bismuth selenide , which can be explained using our theory of doping induced phase transition in topological insulators.
24
Mar '14
Miriam Rafailovich  -  Monday, March 24, 2014
ABSTRACT: In contrast to embryonic stem cells, adult stem cells are subject to differentially small changes in the mechanical, morphological, and chemical cues. The nature of the response may provide us with a better understanding of the role of stem cells in tissue regeneration, wound healing, and aging. Here we discuss how new materials can be engineered where each of these factors can be varied independently such that their influence on stem cell response can be assessed both individually and collectively.
NOTES: CANCELLED
31
Mar '14
ABSTRACT: The first commercial optical communications system was deployed over 30 years ago, since that time new technologies have dramatically enhanced the capabilities of optical networks.  The explosive growth of the Internet has been enabled by these technical innovations, and this trend continues. The early simple point-to-point links have been replaced with systems with more than 105 times more capacity per fiber, connected in a sophisticated mesh network.  This talk will survey the history of optical communications, with special emphasis on recent innovations that enable the optical layer to be more agile than ever before.

Sheryl Woodward received her Ph.D. degree in Physics from Caltech.  For over 25 years she has been in AT&T’s research organization - first with the Crawford Hill Laboratory of Bell Labs Research, and then with AT&T Labs-Research in Middletown, NJ.  She has done research on topics ranging from technologies for cable television to optical networking for continental-backbone networks.  Her current research focuses on software-defined networking for the wide-area network.
7
Apr '14
Steve G. Greenbaum  -  Monday, April 7, 2014
Multinuclear Solid State NMR Studies of Lithium Battery Materials
Department of Physics & Astronomy, Hunter College, CUNY
ABSTRACT: Fundamental materials research is essential to move present-day energy storage technologies to the scale needed to develop all-electric vehicles and to manage intermittent renewable sources such as wind and solar. Comparable advances are also required to develop compact power sources for new medical and military/aerospace applications. Structural studies of materials utilized in lithium battery technology are often hampered by the lack of long-range order found only in well-defined crystalline phases. Powder x-ray diffraction yields only structural parameters that have been averaged over hundreds of lattice sites, and is unable to provide structural information about amorphous compounds. Our laboratory utilizes solid state nuclear magnetic resonance (NMR) methods to investigate structural and chemical aspects of lithium ion cathodes, anodes, electrolytes, interfaces and interphases. NMR is element- (nuclear-) specific and sensitive to small variations in the immediate environment of the ions being probed, for example Li+, and in most cases is a reliably quantitative spectroscopy in that the integrated intensity of a particular spectral component is directly proportional to the number of nuclei in the corresponding material phase. NMR is also a powerful tool for probing ionic and molecular motion in lithium battery electrolytes with a dynamic range spanning some ten orders of magnitude through spin-lattice relaxation and self-diffusion measurements. Brief summaries of several recent NMR investigations will be presented: (i) single crystal studies of LiMPO4 (M = Fe, Co, Ni) lithium ion battery cathodes; (ii) electrode passivation in lithium ion batteries; (iii) charge transfer in hybrid CFx/silver vanadate cathodes for medical devices; (iv) structure and dynamics of disordered fast-ion conducting Li3PS4 electrolytes for Li-S batteries.
28
Apr '14
Jack Harris  -  Monday, April 28, 2014
ABSTRACT: One of the major challenges in physics is to understand how the classical behavior of macroscopic objects emerges in a universe whose laws are fundamentally quantum mechanical. The field of optomechanics attempts to address this issue by studying the quantum behavior of devices in which a macroscopic object’s motion is coupled to individual photons. In the past few years, experiments have demonstrated a number of quantum effects in these devices, including ground-state cooling, entanglement, and the quantum back-action of displacement measurements. I will give an overview of our group's work on these topics. I will also designs for substantially improved optomechanical devices that consist entirely of superfluid helium.
30
Apr '14
Andrey Miroshnichenko  -  Wednesday, April 30, 2014
ABSTRACT: Dielectric nanostructures makes a new twist on light scattering phenomena. Subwavelength particles made of high-dielectric materials exhibit very strong magentic response in visible range, which has been recently demonstrated experimentally. The lower losses, compared to plasmonic counterparts, allow to employ dielectric nanostructures for a variety of applications spanning from optical nanotantennas towards metamaterials. We experimentally demonstrated the suppression of the backward scattering and enhancement of the forward scattering due to superposition of the electric and magnetic dipole excitations of a single element. Moreover, due to othognality of optically induced diplole modes, the scattering pattern is polarization independent. It results in azimuthally symmetric unidirectional scattering which can be achieved even for a single element. Furthermore, directionality can be further enhanced by forming a chain of such elements. Although there is a tradeoff between energy confinement and directionality for different inter-particle distances, the properties of vanishing backward scattering and azimuthal symmetry are always preserved even for random ensembles of such elements. It makes them the perfect candidates for compact low loss optical nanoatennas.
5
May '14
Mikhail Belkin  -  Monday, May 5, 2014
ABSTRACT: Intersubband transitions in n-doped semiconductor heterostructures provide the possibility to quantum engineer one of the largest known nonlinear optical responses in condensed matter systems. I will discuss how we engineer and use these nonlinearities to produce room-temperature terahertz quantum cascade laser sources based on efficient intra-cavity difference-frequency mixing, polaritonic metasurfaces with ultra-fast electrical tuning, and ultra-thin highly-nonlinear metasurfaces for frequency conversion. Structures discussed here represent a novel kind of hybrid metal-semiconductor metamaterials in which exotic optical properties are produced by coupling electromagnetically-engineered resonances in plasmonic nanostructures with quantum-engineered intersubband transitions in semiconductor heterostructures.
7
May '14
John Conway  -  Wednesday, May 7, 2014
The free will theorem
Gorenstein Professor of Mathematics, Queens College (Emeritus, Princeton University)
ABSTRACT: The limited degree of free will required to make a binary decision independent of previous history is also inherent in elementary particles. The proof relies on three uncontested axioms taken from quantum mechanics and relativity theory.
23
Jun '14
Pablo Londero  -  Monday, June 23, 2014
PDFDownload PDF locationSB C201 talk time11:00 am
ABSTRACT: The paint layers of art objects are extremely complex systems, but there are many reasons to improve our ability to characterize them. More sensitive detection of pigments and dyes can provide valuable insights into vanished cultures, and help ensure that proper conservation techniques are applied. A better understanding of protein conformation and fat migration in dried paint layers would shed much-needed light on artistic practices and potential degradation processes. I will give a brief overview of the field and then discuss some current areas of interest in the study of paint layers, with a focus on established and novel applications of surface-enhanced Raman techniques for the identification of colorants.
NOTES: Room SB C201, starts at 11 am
8
Sep '14
Mark Hillery  -  Monday, September 8, 2014
ABSTRACT: Quantum optics arose with the invention of the laser.  Early work focussed on developing a quantum theory of the laser and on better understanding the nature of the quantized electromagnetic field.  It was for this latter work that Roy Glauber won the 2005 Nobel Prize in Physics.  The fields produced by nonlinear optical devices also received attention, because of their unusual correlation properties.  In the 1980's two major areas of study were quantum metrology, using nonclassical states of the electromagnetic field to improve the accuracy of measurements, and micromasers and microlasers, optical devices that are pumped by a single atom at a time.  In the 1990's the field split into three parts.  Some researchers turned their attention to the study of Bose-Einstein condensates and related phenomena in matter-wave physics.  Another group pursued the newly emerging field of quantum information, while a third continued with work on mainstream quantum optics.  Today all of these efforts are alive and doing very well, and they have been joined more recently by the study of quantum opto-mechanics.  A broad overview of these trends will be presented as well as more detailed discussions of some selected topics.
22
Sep '14
Yaron Bromberg  -  Monday, September 22, 2014
ABSTRACT: Coherent backscattering, also known as weak localization,  is one of the most striking examples of the subtle interplay between interference and disorder in scattering samples. Due to constructive interference between time-reversed paths inside the sample, the backscattered intensity exhibits a peak exactly at the direction opposite to the incident wave. Recently we have discovered an analogue of coherent back scattering in multimode optical fibers with strong mode mixing. I will discuss how fibers provide new opportunities to directly access and control the relative phase between the time-reversed paths, allowing us to flip the backscattered peak, and turn it into a dip. I will then show how we utilize correlations between the time-reversed paths for secure optical key distribution.
29
Sep '14
Alexei Tsvelik  -  Monday, September 29, 2014
Strongly correlated systems in low dimensions
Brookhaven National Laboratory
ABSTRACT: I review such aspects of low-D physics as quantum number fractionalization, non-Fermi liquid behavior, and spontaneous mass generation.
6
Oct '14
Lam Hui  -  Monday, October 6, 2014
ABSTRACT: We will discuss the role of symmetries in three different areas of large scale structure: 1. how to test the equivalence principle using black holes in centers of galaxies; 2. how to measure gravitational redshift on cosmological scales using parity-violating signatures in correlation functions; 3. how spontaneously broken symmetries give us non-perturbative relations between different correlation functions. 
20
Oct '14
Sergei Dubovsky  -  Monday, October 20, 2014
ABSTRACT: Advances in X-ray astronomy open the possibility for high precision spin and mass determination for astrophysical black holes starting the era of precision black hole physics. These observations turn astrophysical black holes into sensitive probes of ultra-light axion-like particles motivated by the strong CP problem and string theory.
 When the axion Compton wavelength matches the black hole size, the axions develop "superradiant" atomic bound states around the black hole "nucleus" through the Penrose superradiance process. Their occupation number grows exponentially by extracting rotational energy from the ergosphere, culminating in a rotating Bose-Einstein axion condensate emitting gravitational waves. This transfer of angular momentum from the black hole to the axion condensate results in mass gaps in the spectrum of rapidly rotating black holes and gives rise to distinctive gravity wave signals. 
27
Oct '14
Lea Ferreira dos Santos  -  Monday, October 27, 2014
ABSTRACT: We consider one-dimensional isolated interacting quantum systems that are taken out of equilibrium instantaneously. Three aspects are addressed: (i) the relaxation process, (ii) the size of the temporal fluctuations after relaxation, (iii) the conditions to reach thermal equilibrium. The relaxation process and the size of the fluctuations depend on the interplay between the initial state and the Hamiltonian after the perturbation, rather than on the regime of the system. They may be very similar for both chaotic and integrable systems. The general picture associating chaos with the onset of thermalization is also further elaborated. It is argued that thermalization may not occur in the chaotic regime if the energy of the initial state is close to the edges of the spectrum, and it may occur in integrable systems provided the initial state is sufficiently delocalized.
3
Nov '14
Miriam Rafailovich  -  Monday, November 3, 2014
ABSTRACT: Proton exchange membrane fuel cells (PEMFC) have attracted great attention because of their high power density, low operation temperature ] and almost pollution-free emission . In fuel cells power is generated via the conduction of H+ ions through a polyelectrolyte membrane, commonly composed of sulfonated tetrafluoroethylene based fluoropolymer-copolymer. The function of the fuel cell constitutes a balance between hydrogen oxidation and oxygen reduction reactions where Pt nanoparticles are used to catalyze the reactions at the electrodes . Although the hydrogen oxidation process is a fast electrochemical reaction, challenges come up when impure hydrogen is used. Carbon monoxide is well known to poison the catalyst by blocking active sites on the catalyst’s surface , which prevents the hydrogen adsorption and subsequent oxidation propane, or alcohols can be an inexpensive alternative to pure hydrogen gas, but the high CO and CO2 content of reformed gas, even after purification, poses a major drawback. Hence the ability to engineer a CO resistant system would be a critical step towards enabling the commercialization of a competitively priced hydrogen fuel cell.  We have  developed a technique whereby Au particle nanoplatelets, 3nm in diameter, and only three atomic layers thick, could be reproducibly formed at the air water interface, and then coated onto any arbitrary surface simply by using the LB technique. Here we show that when this layer of NP is deposited directly onto the membrane of a PEM fuel cell, the efficiency of the cell running in ambient conditions is enhanced by more than 80% and an H2 stream with as much as 20% CO2 is tolerated. DFT calculations indicate that a two-step oxidation process is also present in this case, which enables the oxidation reaction to take place in a broad temperature range, extending well below ambient.
17
Nov '14
Premala Chandra  -  Monday, November 17, 2014
ABSTRACT: The development of collective long-range order by means of phase transitions occurs by the spontaneous breaking of fundamental symmetries.  Magnetism is a consequence of broken time-reversal symmetry, whereas superfluidity results from broken gauge invariance.  The broken symmetry that develops below 17.5 kelvin in the heavy-fermion compound URu2Si2 has long eluded such identification.  Here we show that the recent observations of Ising quasiparticles in URu2Si2 results from a spinor order parameter that breaks double time-reversal invariance, mixing states of integer and half-integer spin.  Such "hastatic" order hybridizes uranium-atom conduction electrons with Ising 5f2 states to produce Ising quasiparticles; it accounts for the large entropy of condensation and the magnetic anomaly observed in torque magnetometry.  Hastatic order predicts a tiny transverse moment in the conduction-electron sea, a collosal Ising anisotropy in the nonlinear susceptibility anomaly and a resonant, energy-depedent nematicity in the tunnelling density of states.  We also discuss the microscopic origin of hastatic order, identifying it as a fractionalization of three-body body bound-states into integer spin fermions and half-integer spin bosons.
Work done with Piers Coleman and Rebecca Flint.
References:  PC, P. Coleman and R. Flint Nature 493, 421 (2013)
arXiV: 1404.5920
24
Nov '14
Andrii Golovin  -  Monday, November 24, 2014
ABSTRACT: Metamaterials with properties that vary from point to point in space and time are suitable for new applications such as an “optical cloak”.  Colloidal dispersions of metal nano-rods in dielectric fluids are appropriate to construct such spatially varying and electrically reconfigurable optical metamaterials.  An applied electric field can be used to control the orientation and concentration of nano-rods, and thus modulate the optical properties of the dispersion.  For example, by using gold nano-rods dispersed in toluene, we demonstrate an electrically induced change in refractive index on the order of 0.1 which was used to change the visibility of metal object.  This approach is also valid to design an omnidirectional broadband optical “black-hole”.
23
Mar '15
Felix Izrailev  -  Monday, March 23, 2015
ABSTRACT: Abstract in pdf form is available here.
13
Apr '15
ABSTRACT: A phase-separated approach to reactive oxygen species that employs a liquid at a solid/liquid or solid/gas/liquid interface has been developed. Biphasic and triphasic photosensitizer systems contain regions that are controllably dry, partly wetted, and/or fully wetted. The talk will focus on a superhydrophobic surface fabricated by embedding silicon phthalocyanine sensitizing particles to specific locations on 3-D printed polydimethylsiloxane (PDMS) posts. In the presence of visible light and oxygen, singlet oxygen is formed on the superhydrophobic surface and reacts with an anthracene compound within a freestanding water droplet to produce an endoperoxide. The results indicate that the superhydrophobic sensitizer surface offers a unique system to study reactive singlet oxygen (1O2) transfer routes where a balance of gas and liquid contributions of 1O2 is tunable within the same superhydrophobic surface. Two microphotoreactor devices will also be described. In all, these systems physically isolate the photosensitizer from the solution which may be of practical importance for delivering singlet oxygen for water purification and medical devices.
1. D. Aebisher; D. Bartusik; Y. Liu; Y. Zhao; M. Barahman; Q. Xu; A. M. Lyons; A. Greer "Superhydrophobic Photosensitizers.  Mechanistic Studies of 1O2 Generation in the Plastron and Solid/Liquid Droplet Interface" J. Am. Chem. Soc. 2013, 135, 18990-18998.
2. Y. Zhao; Y. Liu; Q. Xu; M. Barahman; D. Bartusik; A. Greer; A. M. Lyons "Singlet Oxygen Generation on Porous Superhydrophobic Surfaces: Effect of Gas Flow and Sensitizer Wetting on Trapping Efficiency" J. Phys. Chem. A 2014, 118, 10364-10371.
3. D. Bartusik; D. Aebisher; A. M. Lyons; A. Greer "Bacterial Inactivation by a Singlet Oxygen Bubbler: Identifying Factors Controlling the Toxicity of 1O2 Bubbles" Environ. Sci. Technol. 2012, 46, 12098-12104.
4. D. Bartusik; D. Aebisher; B. Ghafari; A. M. Lyons; A. Greer  "Generating Singlet Oxygen Bubbles: A New Mechanism for Gas-Liquid Oxidations in Water" Langmuir 2012, 28, 3053-3060.
5. R. Choudhury; A. Greer "Synergism Between Airborne Singlet Oxygen and a Trisubstituted Olefin Sulfonate for the Inactivation of Bacteria" Langmuir 2014, 30, 3599-3605.
20
Apr '15
Mark Feuer  -  Monday, April 20, 2015
Space: is it the final frontier of photonics?
College of Staten Island of CUNY
ABSTRACT: Fiber optic networks underlie the Internet, massive data centers, and all of the other data-centric services of our modern economy.  The photonics community has sustained prodigious growth in that information flow by increasing the capacity of each optical fiber while simultaneously decreasing the cost per bit transmitted, but recent developments in coherent signaling have brought spectral efficiency close to its theoretical limits, and we are in need of a new revolution.

Space-division multiplexing (SDM), using novel fiber with multiple cores or multiple transverse modes in a large core, is being widely studied as the next wave of fiber optics.  Both multicore and multimode approaches have been successfully demonstrated in research, with the throughput of a single multicore fiber exceeding 1 Pb/s.  Nonetheless, the challenges facing SDM are numerous and daunting.  Multicore fibers are difficult to fabricate, multimode systems are subject to severe inter-modal crosstalk, and successful reduction in the cost per bit will require advanced functional integration of transceivers, amplifiers, mode multiplexers, and other elements of the photonic communications ecosystem.  For efficient network operation, flexible lightpath routing is essential, and SDM offers a number of ways to allocate lightpaths among wavelengths and spatial modes.  Finally, to assure economic viability at all stages of the SDM introduction, a deployment strategy that supports interworking of SDM and non-SDM sections is needed.

In this talk, I will review the past, present, and future of SDM research, and suggest some criteria for a successful commercial introduction of SDM technology. 
27
Apr '15
Emily Rice  -  Monday, April 27, 2015
Exploring exoplanets
College of Staten Island of CUNY
ABSTRACT: Exoplanets are everywhere in the Milky Way Galaxy, and likely the Universe, according to the most recent results from NASA's Kepler mission and other surveys. But how close are we to finding a habitable planet like Earth or to answering the eternal question, Are we alone in the Universe? I will explain how we came to understand the ubiquity of exoplanets, describe the complexity of the current census, and foreshadow what discoveries are likely to lie ahead in the coming years.
18
May '15
Misha Sumetsky  -  Monday, May 18, 2015
Nanophotonics of optical fibres
Aston Institute of Photonic Technologies, Aston University, UK
ABSTRACT: Nanoscale effects in photonic structures fabricated from pure optical fibres are reviewed. In contrast to those in plasmonics, these structures do not contain metal particles, wires, or films with nanoscale dimensions. Nevertheless, a nanoscale perturbation of the fibre radius can significantly alter their performance. I consider slow propagation of whispering gallery modes along the fibre surface. The axial propagation of these modes is so slow that they can be governed by extremely small nanoscale changes of the optical fibre radius. The described phenomenon is exploited in SNAP (Surface Nanoscale Axial Photonics), a new platform for fabrication of miniature super-low-loss photonic integrated circuits with unprecedented sub-angstrom precision. The SNAP theory and applications are reviewed. 
3
Aug '15
Benoît Gérardin  -  Monday, August 3, 2015
PDFDownload PDF locationSB B141
ABSTRACT:

Multiple scattering of waves in disordered media is often seen as a nightmare whether it be for communication, imaging or focusing purposes. The ability to control wave propagation through scattering media is thus of fundamental interest in many domains of wave physics, ranging from optics or acoustics to medical imaging or electromagnetism. Thirty years ago, it was shown theoretically that a properly designed combination of incident waves could be fully transmitted through (or reflected by) a disordered medium. Although this remarkable prediction has attracted a great deal of attention, open and closed channels have never been accessed experimentally.

Here, we study the propagation of elastic waves through a disordered elastic waveguide. Thereby, we present experimental measurements of the full S-matrix across a disordered elastic wave guide. To that aim, laser-ultrasonic techniques have been used in order to obtain a satisfying spatial sampling of the field at the input and output of the scattering medium. The unitarity of the S−matrix is investigated and the eigenvalues of the transmission matrix are shown to follow the expected bimodal distribution. Full transmission and reflection of waves propagating through disorder are obtained for the first time experimentally. The wave-fields associated to these open and closed channels are imaged within the scattering medium to highlight the interference effects operating in each case.

In the second part of the talk, we study beam-like states which can be seen as spatio-temporal open / closed channels. To that aim, the eigenstates of the Wigner-Smith time-delay matrix are considered in a regular cavity and a weakly disordered medium. The propagation of the wave-packets associated to these transmitted trajectory-like states is investigated.

21
Sep '15
Dmitriy Polyansky  -  Monday, September 21, 2015
ABSTRACT: Artificial photosynthetic systems exploit a variety of photochemical transformations with the ultimate result of efficient conversion of the photon energy into chemical bonds. The efficiency of these transformations strongly depends on how successfully proton-coupled electron transfer (PCET) processes are implemented. In our research program we focus on a mechanistic understanding of the role of PCET in reactions such as: (1) photochemical formation and reactivity of NADPH-like transition metal complexes; (2) hydrogen atom transfer (HAT) in the excited states of transition metal systems; (3) transition-metal complexes as photo- and electro-catalysts for proton reduction; and (4) light-driven water oxidation catalyzed by transition metal complexes.

In my presentation I will cover the basic principles of artificial photosynthesis and will explain how simple synthetic models may be used to mimic the action of natural photosystems. I will follow with several examples of catalytic transformations relevant to the production of solar fuels such as water oxidation and the reduction of protons and carbon dioxide. In each of these examples the importance of coupling the movement of multiple equivalents of electrons with proton transfer will be emphasized. Also, the modern time-resolved spectroscopy techniques such as pulse radiolysis and laser flash photolysis will be presented as experimental tools for unraveling complex mechanisms of PCET transformations which take place during catalytic cycles.
28
Sep '15
ABSTRACT: In the past several years our group has been exploring protein energy landscapes in pigment-protein complexes involved in photosynthesis. These complexes offer a unique opportunity to explore native protein environments using optical spectroscopy methods, as chromophores are built into them by nature, without any extraneous manipulations that could potentially alter the structure or dynamics of the protein. Single Molecule (or singe complex) Spectroscopy has recently been a technique of choice for studying spectral dynamics in photosynthetic complexes. However, here I am going to demonstrate that Spectral Hole Burning (SHB) is capable of providing additional or competing information. In particular, most of the spectral shifts observed in single complex experiments are in fact light-induced (and not occurring anyway whether one observes them or not) and thus constitute SHB on a single-molecule level [1]. Analysis of the hole broadening allows us to claim that fast-small shift spectral dynamics in the LH2 complex is specific only to single-complex scenarios and not to the bulk sample. And so on.
Inspired by these results we undertook a detailed SHB study of spectral dynamics in several photosynthetic complexes, with the main focus on the CP43 antenna complex [2] of Photosystem II and dimeric Cytochrome b6f [3]. We also developed a unified approach to modeling SHB and spectral hole recovery, at fixed (burn) temperature and upon thermocycling. This approach relies on the argument that in the presence of “spectral memory” (holes recovering mostly due to burnt systems returning to the pre-burn configuration) the barrier distributions encoded into the non-saturated spectral holes and manifesting during the hole recovery differ from the full true barrier distributions. These partial barrier distributions are vastly different for different shapes of the true full distributions, and one can easily distinguish their manifestations. Quantitatively, all complexes we have explored so far exhibit similar barrier distribution parameters, distinct from those of some simple organic glasses. Qualitatively, however, barrier distribution shapes show great variability. Unlike in CP43 [2], the distributions of barriers between protein sub-states involved in light-induced conformational changes (SHB) in Cytochrome b6f are more likely glass-like ~V^(0.5) (V is the barrier height), and not Gaussian.
There is a high degree of correlation between the heights of the barriers in the ground and excited states in the individual pigment-protein systems, as well as nearly perfect spectral memory. Both spectral hole burning and recovery are due to phonon-assisted tunneling associated with the increase of the energy of a scattered phonon. As the latter is unlikely for simultaneously both the hole burning and hole recovery, proteins must exhibit a NPHB mechanism involving diffusion of the free volume towards the pigment. Entities involved in the light-induced conformational changes are characterized by md2 value of about 1.0.10-46 kg.m2. Thus, these entities are protons or, alternatively, small groups of atoms experiencing sub-Å shifts. However, explaining all SHB and recovery data simultaneously, employing just one barrier distribution, requires a drastic decrease in the attempt frequency to about 100 MHz. This decrease may occur due to cooperative effects.
 
1. Grozdanov, D.; Herascu, N.; Reinot, T.; Jankowiak, R.; Zazubovich, V. J. Phys. Chem. 2010, 114, 3426-3438.
2. Najafi, M., Herascu, N., Seibert, M., Picorel, R., Jankowiak, R., Zazubovich, V., J. Phys. Chem. B 2012, 116, 11780.
3. Najafi, M.; Herascu, N.; Shafiei, G.; Picorel, R.; Zazubovich, V.; J. Phys. Chem. B 2015, 10.1021/acs.jpcb.5b02845
19
Oct '15
Eugene Chudnovsky  -  Monday, October 19, 2015
Random fields and topology
Lehman College of CUNY
ABSTRACT: Recently it has been understood that the effect of random fields on the long-range order in systems with continuous-symmetry order parameter is controlled by topology. The n-component order parameter in d dimensions, interacting with the random field, exhibits glassy behavior at n < d + 1 due to the pinning of singularities.  Nonsingular topological objects at n = d + 1 provide weak metastability. At n > d + 1 topological defects are absent and the behavior of the system is fully reversible, characterized by the exponential decay of correlations. Topological arguments have been confirmed numerically on lattices of up to one billion sites. Along these lines the effects of magnetic impurities on the ferromagnetic order and random anisotropy effects in amorphous and sintered magnets have been studied. Our findings also shed new light on properties of pinned charge density waves and properties of pinned flux lattices in superconductors. This research is supported by the U.S. Department of Energy through grant No. DE-FG02-93ER45487.
 
1. D. A. Garanin, E. M. Chudnovsky, and T. C. Proctor, The Role of Vortices in the Three-Dimensional Random-Field XY Model, Europhysics Letters 103, 67009 (2013).                                                                             
2. D. A. Garanin, E. M. Chudnovsky, and T. C. Proctor, Random-Field XY Model in Three Dimensions, Physical Review B  88, 224418 (2013).                
3. T. C. Proctor, D. A. Garanin, and E. M. Chudnovsky, Random Fields, Topology, and the Imry-Ma Argument, Physical Review Letters 112, 097201 (2014).                                                                                                  
4. D. A. Garanin and E. M. Chudnovsky, Ordered vs Disordered States of the Random-Field Model in Three Dimensions, European Physics Journal B 88, 81 (2015).                                                                                           
5. T. C. Proctor, E. M. Chudnovsky, and D. A. Garanin, Scaling of Coercivity in a 3d Random Anisotropy Magnet, Journal of Magnetism and Magnetic Materials 384, 181 (2015).                                                              
6. T. C. Proctor and E. M. Chudnovsky, Effect of Dilute Random Field on Continuous Symmetry Order Parameter, Physical Review B 91, 140201(R) (2015). 
26
Oct '15
Mikael Rechtsman  -  Monday, October 26, 2015
Aspects of photonic topological insulators
Pennsylvania State University
2
Nov '15
Victor Yakovenko  -  Monday, November 2, 2015
Economic inequality from a statistical physics point of view
Department of Physics, University of Maryland, College Park
ABSTRACT: Similarly to the probability distribution of energy in physics, the probability distribution of money among the agents in a closed economic system is also expected to follow the exponential Boltzmann-Gibbs law, as a consequence of entropy maximization.  Analysis of empirical data shows that income distributions in the USA, European Union, and other countries exhibit a well-defined two-class structure.  The majority of the population (about 97%) belongs to the lower class characterized by the exponential ("thermal") distribution.  The upper class (about 3% of the population) is characterized by the Pareto power-law ("superthermal") distribution, and its share of the total income expands and contracts dramatically during booms and busts in financial markets.  Globally, data analysis of energy consumption per capita around the world shows decreasing inequality in the last 30 years and convergence toward the exponential probability distribution, in agreement with the maximal entropy principle. Similar results are found for the global probability distribution of CO2 emissions per capita.  All papers are available at http://physics.umd.edu/~yakovenk/econophysics/.  For recent coverage in Science magazine, see http://www.sciencemag.org/content/344/6186/828
9
Nov '15
Lia Krusin  -  Monday, November 9, 2015
16
Nov '15
Allyson Sheffield  -  Monday, November 16, 2015
ABSTRACT: Where did stars in the Milky Way's halo form? The LCDM model predicts that the Milky Way's halo was built in a "bottom-up" fashion, and this view is now generally accepted due to overwhelming evidence of the relics of past mergers. It is still uncertain, however, what fraction of the halo is made up of such accreted debris. Close to the time of accretion, a group of stars formed in a particular satellite of the Milky Way will show coherence spatially, kinematically, and chemically. In the inner halo where dynamical timescales are short, spatial coherence will become blurred quickly, although kinematical and chemical coherence remain. Kinematics alone may still lead to ambiguity, as a merger event can cause stars formed in the Milky Way to redistribute into rings in the halo ("kicked out" disk stars) and these rings can be difficult to distinguish from accreted satellite stars. Thus, to get a more complete profile of a star's formation history, both kinematical and chemical information are needed.
 
I will report chemical abundances for a sample of M giants in the inner halo of the Milky Way. Abundances are derived for a-elements and neutron capture elements. By analyzing the multi-dimensional abundance space, the formation site of the halo giants – in-situ, kicked-out disk, or accreted – can be assessed. Additionally, I will report results from a study to understand the origin of a diffuse cloud of stars known as Triangulum-Andromeda.
23
Nov '15
Mishkat Bhattacharya  -  Monday, November 23, 2015
ABSTRACT: This talk will focus on optomechanics, i.e. the interaction of mechanical motion with modes of the electromagnetic field. Optomechanics is currently at the frontier of physics research as an enabler of fundamental investigations into macroscopic quantum mechanics, as well as a platform for next-generation ultrasensitive measurement devices. The first half of this talk will introduce the subject by reviewing results in cavity optomechanics, namely the interaction of mechanical motion with electromagnetic modes confined to resonators. Of chief interest will be degrees of vibrational, torsional and free rotational mechanical motion as well as polarization and orbital angular momentum-carrying optical beams. The second half of the talk will consider cavityless optomechanical systems, which are distinguished by the absence of a resonator, the presence of ultralow damping, and the use of highly nonlinear feedback. In this context we will describe our theoretical modeling of the optical levitation experiments being carried out in the group of our collaborator Prof. A. N. Vamivakas at the Institute of Optics, University of Rochester.
30
Nov '15
Alexander Lisyansky  -  Monday, November 30, 2015
2
Dec '15
Alexey Slobozhanyuk  -  Wednesday, December 2, 2015
Metamaterials-inspired technologies for improvement of Magnetic Resonance Imaging
Australian National University, ITMO University, Russia
ABSTRACT: I will review briefly my recent activities in the field of microwave metamaterials. The main scientiffic part of my talk will be devoted to the application of metamaterials for Magnetic Resonance Imaging (MRI). In particular, I will show how to exploit efficiently the unique properties of an ultrathin metasurface resonator for improving the magnetic resonance imaging [1]. A metasurface is formed by an array of metallic wires placed inside the MRI scanner under the object. By means of subwavelength near-field manipulation  with  the metasurface, it is possible to enhance and redistribute the  radiofrequency magnetic field  in the region of interest, strongly  improving scanner sensitivity, signal-to-noise ratio, and image  resolution.
 
[1] A. P. Slobozhanyuk, A. N. Poddubny, A. J. E. Raaijmakers, C. A. T. van den Berg, A. V. Kozachenko, I. A. Dubrovina, I. V. Melchakova, Yu. S. Kivshar, P. A. Belov, "Enhancement of magnetic resonance imaging with metasurfaces", arXiv:1507.01411 (2015).
7
Dec '15
Pier Mello  -  Monday, December 7, 2015
14
Dec '15
Luat Vuong  -  Monday, December 14, 2015
16
Dec '15
Matthieu Davy  -  Wednesday, December 16, 2015
ABSTRACT: The transmission matrix provides the fullest account of transmission through multichannel samples. The distribution of transmission eigenvalues gives the degree to which the transmission can be controlled.  Remarkably, open and closed channels exist in the diffusion regime in contrast to the diffusion picture of incoherent transmission. This means that an incident wavefront can be shaped so that the energy is completely transmitted or completely reflected. I will show that those channels make it possible to tailor the energy density inside the sample and provide a way to achieve a deep penetration of the energy. Those results extend our knowledge of the waves from the interfaces to the interior of random samples.
8
Feb '16
Sergey Vitkalov  -  Monday, February 8, 2016
ABSTRACT: The quantization of electron motion in magnetic fields generates a plethora of fascinating phenomena observed in condensed materials. One of the well-known examples is the Shubnikov-de Haas (SdH) resistance oscillations. In two dimensional electron systems, SdH oscillations can be very pronounced leading to the Quantum Hall Effect (QHE) at low temperatures. 

Landau quantization produces a remarkable effect on Joule heating of two dimensional (2D) electrons. The heating forces 2D electrons into exotic electronic states in which voltage (current) does not depend on current (voltage). In contrast to the linear response at low temperatures (SdH, QHE), the quantization affects Joule heating in a significantly broader temperature range. At temperatures significantly exceeding the cyclotron energy the dc heating produces a multi-tiered electron distribution containing as many tiers as the number of Landau levels inside the energy interval kT. This quantal heating preserves the overall broadening of the electron distribution. Surprisingly the distribution resulting from quantal heating is, in some respect, similar to the one created by the quantum microwave pumping between Landau levels. Indicated phenomena produce a broad variety of nonlinear effects in quantizing magnetic fields and present an exciting area of the contemporary research. In this talk a recent experimental investigations of the dynamics of quantal heating are presented indicating an important role of the electron-electron interaction in the relaxation of the electron distribution.  
29
Feb '16
Katherine Willets  -  Monday, February 29, 2016
ABSTRACT: Noble metal nanoparticles can support localized surface plasmons, which lead to enhanced electromagnetic fields at the nanoparticle surface and allow for a host of surface-enhanced spectroscopies, such as surface-enhanced Raman scattering (SERS).  While extensive theoretical calculations have been performed that predict how these enhanced electromagnetic fields are distributed on the nanoparticle surface, confirming these results using optical techniques is extremely challenging due to the diffraction limit of light.  Because the metal nanoparticles are smaller than the wavelength of light, they appear as diffraction limited spots in optical images, obscuring the local electromagnetic field enhancements.  This talk will describe recent efforts to use high resolution single molecule imaging techniques to measure how electromagnetic fields are locally enhanced on the surface of noble metal nanoparticles for applications in SERS.  Single molecule spectroscopy allows us to beat the diffraction limit by over an order of magnitude, providing the necessary resolution to optically image electromagnetic field enhancements on noble metal nanoparticle surfaces.
7
Mar '16
Alexander Gaeta  -  Monday, March 7, 2016
21
Mar '16
Sumita Pennathur  -  Monday, March 21, 2016
ABSTRACT: Rapidly evolving acute respiratory infectious diseases (for example, Influenza, Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), and West Nile Flavivirus (WNF)) now have significantly deleterious impacts on human health and economic productivity worldwide. Due to their highly contagious nature, and rapid negative impact on human health and economies, these diseases require developing a simple, high throughput, and immediate (within 30 minutes) screening methodology that can affordably and accurately determine virus diagnosis, so that treatments can be administered in a timely fashion. Furthermore, the expense of anti-virals now prohibits broad distribution even in developed countries. The diagnostic approaches that we are developing in the Pennathur lab enables rapid regionally based deployment of medications to stymie the spread of viruses. These approaches include (1) the development of a nanofluidic conductivity sensor for general nucleic acid detection, (2) fluorescent silver nanocluster DNA probes (AgNC-DNA) combined with microfluidic capillary electrophoresis (mCE), to detect and identify DNA sequences from HepA, HepB and HepC viruses, and (3) microfluidic tangential flow filtration (μTFF) of blood and serum for efficient on-chip sample preparation. 

Specifically, we have developed a novel nanofluidic-based platform for the efficient detection of nucleic acids. The transduction method is label-free, inducing the formation DNA complexes that result in changes in flow velocity and current in a nanofluidic channel. This innovation takes into account the changes in surface and bulk conductivity in a nanochannel due to the concentration of ions in the bulk. Furthermore, we have developed a method for modifying a low cost, molecular beacon-like AgNC-DNA probe so that multiple DNA sequences can be detected and identified simultaneously and rapidly using microfluidic capillary electrophoresis. As a demonstration, we used this technique to design probes for nucleic acid targets of Hepatitis A, B and C virus. Finally, to truly make this work translational, we have developed a microfluidic based method for biological sample filtration. Such a method allows for facile integration with the above diagnostic sensors, and uses tangential flow filtration methods to effectively isolate targets of interest. 
28
Mar '16
Steven Anlage  -  Monday, March 28, 2016
ABSTRACT: Because of the possibility of electromagnetic interference between neighboring electronic systems, there is an urgent need to quantify the entry and distribution of electromagnetic (EM) energy within complicated metallic enclosures and to understand the manner in which this energy couples to sensitive electronic devices within such enclosures.  When the wavelength of the impinging radiation is much smaller than the typical length scale of the enclosure, the distribution of energy within such cavities is highly sensitive to small changes in the frequency, the structure of the cavity, as well as the nature of the channels which couple EM energy into the cavity.  Thus, a statistical approach to understanding this problem is called for.  
There is great interest in the wave and quantum properties of systems that show chaos in the classical (short wavelength) limit.  These ‘wave chaotic’ systems appear in many contexts: nuclear physics, acoustics, two-dimensional quantum dots, and electromagnetic enclosures, for example. Random Matrix Theory (RMT) predicts the universal fluctuating properties of quantum/wave systems that show chaos in the classical/ray limit.  
In this context we developed a stochastic model, the “Random Coupling Model” (RCM) [1,2], which can accurately predict the probability density functions (PDFs) of voltages and electromagnetic field quantities on objects within such cavities, given a minimum of information about the cavity and the nature of its internal details.   The RCM is formulated in terms of electrical impedance, essentially equivalent to Wigner’s reaction matrix in quantum mechanics, rather than the more commonly studied scattering matrix.  The RCM predictions have been tested in a series of experiments using normal metal and superconducting quasi-two-dimensional and three-dimensional electromagnetic billiards [3].  We have extended the RCM in a number of directions, for example by examining the effects of ‘short orbit’ ray trajectories that enter the cavity, bounce a small number of times, and then leave the cavity.  We are able to account for the effects of these orbits using a semi-classical theory, and find excellent agreement between theory and experiment [4].  Our current efforts are focused on testing predictions for the statistical properties of multiple inter-connected enclosures [5], enclosures irradiated through apertures [6], and enclosures characterized by a mixed chaotic and regular phase space [7], using scaled model structures.
For more information see: http://anlage.umd.edu/AnlageQChaos.htm

[1] S. Hemmady, et al., Phys. Rev. Lett. 94, 014102 (2005).
[2] X. Zheng, T. M. Antonsen and E. Ott, Electromagnetics 26, 3 (2006); Electromagnetics 26,     37 (2006).
[3]  S. Hemmady, et al., IEEE Trans. Electromag. Compat. 54, 758-771 (2012); Z. B. Drikas, et     al., IEEE Trans. Electromag. Compat. 56, 1480-1487 (2014).
[4]  J.-H. Yeh, et al.,  Phys. Rev. E 81, 025201(R) (2010); Phys. Rev. E 82, 041114 (2010). 
[5]  G. Gradoni, et al., Phys. Rev. E 86, 046204 (2012).
[6]  G. Gradoni, et al., IEEE Trans. Electromag. Compat., 57, 1049-1061 (2015).
[7]  Ming-Jer Lee, et al., Phys. Rev. E 87, 062906 (2013).
30
Mar '16
Sergey Makarov  -  Wednesday, March 30, 2016
ABSTRACT: ​The resonant metallic nanoparticles are proven to be efficient systems for the electromagnetic field control at nanoscale, owing to the ability to localize and enhance the optical field via excitation of strong plasmon resonances. In turn, high refractive index dielectric nanoparticles with low dissipative losses in the visible range, possessing magnetic and electric Mie-type resonances, offer great opportunity for light control via designing of scattering properties. Such resonant nanoparticles made of high refractive index dielectrics (Si, Ge etc.) revolutionized the field of nanophotonics, opening a new branch – All-dielectric Nanophotonics. In this talk, we will discuss recent advances in the all-dielectric and hybrid (metal/dielectric) nanophotonics, including such effects as nonlinear reconfiguration of nanoparticle scattering properties and enhanced optical frequency conversion. Additionally, I will present our novel methods for fabrication of resonant all-dielectric and hybrid nanoparticles.
4
Apr '16
Hakan Tureci  -  Monday, April 4, 2016
11
Apr '16
I. Cevdet Noyan  -  Monday, April 11, 2016
ABSTRACT: 100-plus years of theoretical and experimental advances have reduced kinematical scattering formalisms for powder diffraction to routine, vendor-supplied, black-box analysis programs accessible to users at all training levels. Understanding what really goes on in the analysis, however, is a non-trivial task. We used computer modeling to analyze the powder diffraction process from nanoparticle ensembles.
Our results showed, surprisingly, that the classical formulations described in diffraction textbooks were inadequate; venerable concepts like reflection multiplicity, the "Lorentz factor", sampling statistics, etc. actually depended on the size of the crystalline particles contributing to the diffraction profile. We expect modeling of scattering experiments to yield more surprises as the phase space hidden behind canonical assumptions becomes accessible for exploration.
18
Apr '16
Michael Shara  -  Monday, April 18, 2016
The Nova-Supernova Connection
American Museum of Natural History
ABSTRACT: Classical novae and supernovae were long thought to be completely separate astrophysical phenomena. This is no longer true; at least some supernovae may have symbiotic nova precursors. I’ll review the current state of  knowledge of the temporal evolution of the white dwarfs in novae, and the Tree of Death of Supernovae. These will help illuminate the still-controversial but ultimately testable, hypothesized connection between novae and supernovae.
2
May '16
Saima Husaini  -  Monday, May 2, 2016
ABSTRACT: In recent years, graphene has emerged as a potential material in optoelectronic devices ranging from optical modulators, photodetectors to saturable absorbers for mode-locking lasers. Significant effort has also been made to develop graphene-based materials and devices for biotechnological applications such as biosensors, drug delivery, cell imaging and detection.
The aim of this talk is to introduce the optoelectronic properties of graphene and possible applications to various devices. The devices covered will range from nonlinear optical devices such as optical limiters and saturable absorbers for mode-locking lasers, to graphene field effect transistors (FETs) for chemical sensing. 
9
May '16
Xiaojun Cheng  -  Monday, May 9, 2016
13
May '16
Oleg Tretiakov  -  Friday, May 13, 2016
ABSTRACT: Manipulating small spin textures that can serve as bits of information by electric currents is one of the main challenges in the field of spintronics. In this work we study the stability and current driven dynamics of Skyrmions and their lattices in two-dimensional ferromagnets [1,2] and antiferromagnets [3] with Dzyaloshinskii-Moriya interaction.
 
Ferromagnetic Skyrmions recently attracted a lot of attention because they are small in size and are better than domain walls at avoiding pinning sites while moved by electric current. Nevertheless, ferromagnetic Skyrmions also have certain disadvantages, such as the presence of stray fields and transverse dynamics, making them harder to employ in spintronic devices. To avoid these unwanted effects, we propose a novel topological object: the antiferromagnetic (AFM) Skyrmion [3] and explore its properties using analytical theory based on generalized Thiele equation and micromagnetic simulations. This topological texture has no stray fields and we show that its dynamics are faster compared to its ferromagnetic analogue. We obtain the range of stability and the dependence of AFM Skyrmion radius on the strength of Dzyaloshinskii-Moriya interaction coming from relativistic spin-orbit effects.
 
Moreover, we study the temperature effects on the stability and mobility of AFM Skyrmions. We find that the thermal properties, e.g. such as the antiferromagnetic Skyrmion radius and diffusion constant, are rather different from those for ferromagnetic Skyrmions. More importantly, we show that due to unusual topology the AFM Skyrmions do not have a velocity component transverse to the current (no topological Hall effect), and thus may be interesting candidates for spintronic memory and logic applications.
 
[1] I. A. Ado, O. A. Tretiakov, M. Titov, arXiv:1603.07994 (2016).
[2] U. Gungordu, R. Nepal, O. A. Tretiakov, K. Belashchenko, and A. A. Kovalev, Phys. Rev. B 93, 064428 (2016).
[3] J. Barker and O. A. Tretiakov, Phys. Rev. Lett., 116, 147203 (2016).
16
May '16
Garnett Bryant  -  Monday, May 16, 2016
15
Aug '16
Klaus Ziegler  -  Monday, August 15, 2016
ABSTRACT: A spatially varying gap leads to the creation of edge states. These very robust states are associated with quantized currents, the foundation of the quantum Hall effect in electronic systems. Here we discuss a randomly distributed gap in photonic systems. Despite the presence of strong disorder, the behavior of photons is not characterized by conventional Anderson localization: Rather than confining the photons to an area of the size of the localization length, the random gap creates geometric states. This type of confinement can be understood as angular localization, where the photons of a local light source can propagate only along waveguides in certain directions. The directions are determined by the boundary of the spectrum. Thus, the system's properties on the shortest scales determine the behavior of the photon propagation on the largest scales.
23
Aug '16
Martin Moskovits  -  Tuesday, August 23, 2016
19
Sep '16
ABSTRACT: Light scattering from non-spherical particles and aggregates exhibit complex structure that is revealed only when observed in two angular dimensions. However, due to variations in shape, packing, and orientation of such aerosols, the structure of two-dimensional angular optical scattering (TAOS) patterns varies among particles. The spectral dependence of scattering contributes further to the observed complexity, but offers another facet to consider. By leveraging multispectral TAOS data from flowing aerosols, we have identified novel morphological descriptors that may be employed in multivariate statistical algorithms for “unknown" particle classification. While these descriptors provide a means for grouping particles as a class, they provide little information about particle orientation. For this, we implement digital holography, which can be recorded simultaneously with TAOS data on a single camera to enhance particle characterization. This talk will discuss the underlying principles behind the two strategies and their synergy for particle characterization.
26
Sep '16
Victor Gopar  -  Monday, September 26, 2016
ABSTRACT: Disorder effects on the transport of classical and matter waves (EM & electrons, for instance) have been widely investigated from fundamental and practical points of view. It is widely believed that the presence of disorder in 1D random media leads to an exponential spatial localization of waves, i.e., Anderson localization. We have recently proposed, however, a model of disorder that induces anomalous localization or delocalization of electrons in disordered quantum wires. Following that model, we provide experimental evidence demonstrating that anomalous localization of electromagnetic waves can be induced in microwave waveguides with dielectric slabs randomly placed: if the random spacing between the slabs follows a distribution with a power-law tail (Lévy-type distribution), unconventional properties in the microwave-transmission fluctuations take place revealing the presence of anomalous localization. We obtain both theoretical and experimental distributions of the transmission through random waveguides and show that only two parameters, both of them experimentally accessible, determined the complete transmission distribution.

Concerning matter waves (electrons), numerical simulations of disordered armchair graphene nanoribbons reveal the presence of anomalous electron localization, while the statistical properties of the conductance are also described by our model.

In this talk we will give some general and basic ideas of our theoretical framework (random-matrix theory) for describing wave transport phenomena in the presence of standard-Anderson and anomalous localizations.
7
Nov '16
Orly Levitan  -  Monday, November 7, 2016
ABSTRACT:
Despite the fact that there are still abundant natural petroleum reserves (supplies will last for more than a century), significant carbon mitigation cannot be achieved without the development of environmentally sustainable and renewable fuels. Owing to their high productivity-to-biomass ratio, ease of cultivation, and ability to grow in saline water, algae have been considered as a leading biodiesel feedstock. To displace fossil fuels, however, algae must be grown at a scale that yields approximately 10 million barrels of oil per day – which would supply approximately 50% of the total U.S. consumption. For the last few decades, researchers have searched for the “sweet spot” between algae’s triacylglycerols (TAG) production and biomass accumulation to obtain a strain with increased lipid production that can be developed as a commercially viable algal feedstock for biofuel production. Diatoms, a unique algal taxon, naturally accumulate TAGs as storage components, which can be readily converted to biodiesel. In fact, lipids derived from fossil diatoms are a major component of the highest quality petroleum.  Therefore fast growing, lipid accumulating, diatoms can be an excellent platform for biodiesel production. For many years, studies have been performed to environmentally optimize diatoms’ lipid production and biomass accumulation, yet no economically sustainable strain has been reported. In my talk, I will present our unique, genetically modifies, strains generated from the model diatom Phaeodactylum tricornutum, that could be used as a test-case for economical sustainable biofuel production. These strains are characterized by high lipid yield, yet keep relatively fast growth rates and are more efficient in using solar energy for lipid production.
9
Nov '16
Sharon Loverde  -  Wednesday, November 9, 2016
21
Nov '16
Petr Shibayev  -  Monday, November 21, 2016
28
Nov '16
Stephen Pekar  -  Monday, November 28, 2016
PDFDownload PDF locationC201 talk time12:15 pm
30
Nov '16
5
Dec '16
Kazuhiko Uebayashi  -  Monday, December 5, 2016
ABSTRACT: Magnetic binary alloy, iron rhodium (FeRh), has attracted attention since 1938. It is known to exhibit a magnetic phase transition from a ferromagnetic to an antiferromagnetic state at 350 K. While its crystal structure remains unchanged at the transition, its volume undergoes a 1% increase. In this talk, we present our studies of several magnetic binary alloys related to FeRh: FePd, MnRh, MnPd, and FePt, using first-principles calculations based on the linear muffin-tin orbital approach. Our results, which agree with several experiments and calculations, suggest that our approach well describes the crystal and magnetic structures of these binary alloys in their ground states and the structures of the related pseudo-binary alloys. However, our treatment of the magnetic phase transition has thus far not incorporated the effects of temperature due to a limitation in our code. In order to take account of these thermal effects, we present an approach that combines first-principles and quantum field theoretical methods.
1
Mar '17
ABSTRACT: Understanding ultrafast carrier photophysics including photogeneration, recombination, transport, and energy transfer is the foundation of nanostructured material electronic and optoelectronic applications. Nanocrystals constitutes a major class of nanostructured material. They have unique physics property due to strong quantum confinement effect that leads to multiple exciton generation (MEG) effect where more than two pairs of exciton generated by absorbing one photon, and strong multiple exciton interactions that lead to Auger recombination. While the majority research groups rely on all optical spectroscopies to understand novel photophysics, I use a unique ultrafast photocurrent spectroscopy (sub-40 ps) by directly collecting photocurrent in situ devices. In this talk, I will demonstrate this unique ultrafast photocurrent spectroscopy (which can be developed to sub- 1ps) to bridge the gap between fundamental photophysics and applied devices research. In addition to nanocrystals, I will demonstrate carrier transport dynamics study in 2D materials of black phosphorus
8
Mar '17
Andreas Stier  -  Wednesday, March 8, 2017
ABSTRACT: In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Due to heavy band masses and large exciton binding energies in the newly discovered class of 2D semiconductors, such as monolayer WSe2 or MoS2, low-magnetic field studies have to date not revealed the majority of these properties.   
 
In this talk, I will describe our results on low-temperature, circularly polarized magneto-optical spectroscopy on atomically-thin semiconductors in pulsed magnetic fields to 65 Tesla [1, 2].
 
After a brief introduction of the field of 2D semiconductors, I will present our results on the valley Zeeman splitting of both the A and the B excitons in WS2. We find effective valley g-factors = -4.0 for both excitons. This unexpected and surprising result suggests that the valley Zeeman effect in these 2D semiconductors originates primarily from the atomic orbital magnetic moment alone – that is, the much-discussed Berry curvature in TMDs, appears to have minimal influence [1].
 
More importantly, the use of large magnetic fields allowed the first observation of the small quadratic diamagnetic shift of excitons in these materials. Diamagnetic shifts provide a direct experimental measure of the exciton size, and I will discuss how we can use this parameter to estimate the large exciton binding energies [1].
Lastly, I will discuss how we can tune the exciton size, and therefore the binding energy, in 2D materials by tuning the dielectric screening of the environment [2].

This work highlights how the dielectric screening of the environment influences 2D excitons and therefore aids in the smart design of novel optoelectronic devices that exploit the unique physics of van der Waals heterostructures.  
 
[1] A. V. Stier et al., Nat. Comm. 7, 10643 (2016).
[2] A. V. Stier et al., Nano Lett. 16, 7054 (2016)
13
Mar '17
Euclides Almeida  -  Monday, March 13, 2017
ABSTRACT: In nonlinear optics, we study the material response to excitation by intense optical fields. Phenomena such as harmonic generation, ultrafast laser spectroscopy and super-resolution microscopy, have all emerged from fundamental understanding of the nonlinear material response.

In this talk, I will discuss how nanostructures provide a fertile ground for nonlinear optical interactions, and how “squeezing” light to the nanometric regime gives rise to unforeseen nonlinear phenomena and photonic devices with unmatched functionalities. By using modern nanofabrication tools such as focused ion beam and additive electron beam nanolithography, we can rationally design nanostructures to selectively enhance the nonlinear response and efficiently generate coherent optical beams at new optical frequencies. The nanoscale control over the phase of the optical waves leads to new implementation of the basic physical laws governing electromagnetic wave interactions, leading the way towards the realization of integrated photonics devices that can simultaneously generate and shape light beams. Using these ideas, we have recently demonstrated holograms that produce a “floating” visible image when illuminated by an invisible beam, and multi layered plasmonic devices with unique optical functionalities. Prospects for the incorporation of precise nonlinear phase control with state-of-the-art nanofabrication for fundamental studies and for practical device applications will be discussed.

[1] E. Almeida and Y. Prior. Scientific Reports 5, 10033 (2015)
[2] E. Almeida, G. Shalem and Y. Prior. Nature Communications 7, 10367 (2016)
[3] E. Almeida, O. Bitton and Y. Prior. Nature Communications 7, 12533 (2016)
[4] O. Avayu*, E. Almeida*, Y. Prior and Tal Ellenbogen. Nature Communications, in press (2017)
20
Mar '17
Akashdeep Kamra  -  Monday, March 20, 2017
ABSTRACT: Recent experimental advances in generation and detection of pure spin currents have opened up new avenues for exploiting magnets for technology as well as for exciting fundamental physics. Exotic quasiparticles have been observed in complex spin systems exhibiting spin ice rules, skyrmions etc. In this talk, I will discuss emergence of novel quasiparticles, mediated by magetic dipolar interactions, that have been hiding in simpler spin systems with uniformly ordered ground states.
Amongst other properties, these quasiparticles exhibit spin ranging from zero to above 1. These exotic excitations can be interpreted as quantum coherent conglomerates of magnons, the eigen-excitations when the dipolar interactions are disregarded. Of particular interest is our finding that the eigenmodes in an easy-axis antiferromagnet are spin-zero quasiparticles instead of the widely believed spin 1 magnons. The latter re-emerge when the symmetry is broken by a sufficiently large applied magnetic field. The spin greater than 1 is accompanied by vacuum fluctuations and may be considered a weak, non-geometrical form of frustration.
27
Mar '17
Michael Shlesinger  -  Monday, March 27, 2017
29
Mar '17
David Pile  -  Wednesday, March 29, 2017
How to publish at Nature Photonics
Senior Editor, Nature Photonics
PDFDownload PDF coffee time12:00 pm talk time12:15 pm
ABSTRACT: Nature journals in the physical sciences will be discussed with particular emphasis on Nature Photonics. Historic data of submissions and acceptances will be shown, showing some strong geographic trends. The importance of cover letters, what makes a useful referee report, how to appeal (and how not to appeal), and other types of opportunities for getting published in Nature Photonics (Reviews, Correspondence, Commentary, etc.) will be covered. Bring all of your tough questions.
30
Mar '17
Diederik Wiersma  -  Thursday, March 30, 2017
Photonics Walking Up a Human Hair
National Institute for Metrology Research (INRIM) European Laboratory for Non-linear Spectroscopy (LENS) and Univ. of Florence, Italy
ABSTRACT: I will report on a new research line in which nano photonics is combined with deformable micro structures. In particular, I will discuss how liquid crystal elastomers can be used to make deformable photonic components, where light induces structural deformations that feed back on the optical properties of the structure. Also I will show how such concepts can be used to make functional microscopic structures that can perform simple tasks and move around (walk/swim), using the environmental light as energy source. Nature is a source of inspiration for many of the designs used in this context.
NOTES: Cancelled
3
Apr '17
Mirco Milletari  -  Monday, April 3, 2017
ABSTRACT: Spintronics, the science that aims at utilising the spin degrees of freedom in addition to the charge of electrons for low-power operation and novel device functionalities, has seen rapid developments in the past decade. In particular, the Spin Hall (SH) effect, i.e. the emergence of a transverse spin current in response to an applied longitudinal electric field, has attracted much interest for the possibility of building all-electric Spin manipulation devices [1]. The effciency of the Spin current generation is measured by the SH angle. While in semiconductors the SH angle is quite small (0.0001-0.001) [2], it was shown that a giant SH conductivity can be achieved in Graphene decorated with small doses of resonant, Spin orbit active adatoms [3]. It was argued that in this case, the e_ect is mostly due to the semiclassical Skew scattering mechanism, where electrons of di_erent spins are scattered asymmetrically. 

In this talk, I will present present a rigorous microscopic theory of the extrinsic spin Hall effect in disordered graphene based on a nonperturbative quantum diagrammatic treatment incorporating skew scattering and anomalous {impurity concentration-independent{ quantum corrections on equal footing [4, 5]. Our self-consistent approach {where all topologically equivalent noncrossing diagrams are resummed - unveils that the skewness generated by spin-orbit-active impurities deeply inuences the anomalous component of the SH conductivity, even in the weak scattering regime. This seemingly counterintuitive result is due to the symmetry structure induced by spin-orbit coupling, for which the commonly Gaussian white noise approximation is generally invalid. Our treatment shows that it is possible to experimentally access regions in parameter space where anomalous quantum contributions to the SH conductivity are dominant.

Finally, we assess the role of quantum interference corrections by evaluating an important subclass of crossing diagrams, considered only recently in the context of the anomalous Hall effect [6]. We show that diagrams encoding quantum coherent skew scattering events, display a strong Fermi energy dependence, dominating the anomalous spin Hall component away from the Dirac point. Our findings open up the intriguing prospect of measuring quantum interference fingerprints in nonlocal spin signals. 

[1] J. Sinova, S. O. Valenzuela, J. Wunderlich, C. H. Back, T. Jungwirth, Rev. Mod. Phys. 87 (2015).
[2] Y. K. Kato, R.C. Myers, A.C. Gossard and D. D. Awschalom, Science 306, 1910 (2004).
[3] A. Ferreira, T. G. Rappoport, M. A. Cazalilla, and A. H. Castro Neto, Phys. Rev. Lett. 112, 066601 (2014).
[4] M. Milletar__ and A. Ferreira, Phys. Rev. B 94, 201402(R) (2016)
[5] M. Milletar__ and A. Ferreira, Phys. Rev. B 94, 134202 (2016)
[6] A. Ado, I.A. Dmitriev, P. M. Ostrovsky and M. Titov, EPL 111, 37004 (2015).
24
Apr '17
Diana Bratu  -  Monday, April 24, 2017
ABSTRACT: Research efforts to better understand the regulation of mRNA are afoot worldwide, with one of the key challenges being the visualization of mRNA and how it interfaces with these proteins to influence the expression of important genes. We are contributing to this field through a gamut of unique biophotonic methods, from probe design to advanced imaging approaches, thus improving upon the detection and accuracy of mRNA visualization and its co-localization with trans-acting proteins important for the normal function of processes within a cell.
Using Drosophila melanogaster (the fruit fly) as a model organism, my research group employs fluorescent probes and spinning disc confocal microscopy to track the movement of mRNA and proteins throughout the egg chamber. We employ genetically encoded fluorescent proteins and short molecular probes (i.e. molecular beacons) allowing for the detection of various endogenous proteins and mRNAs, thus enabling real-time tracking of these molecules as they are transported within the cell. While this has obvious implications for the research of oogenesis, these studies act as a biologic proof of principle to guide other researchers¹ studies examining mRNA transport in other systems.
26
Apr '17
Miquel Rude*  -  Wednesday, April 26, 2017
ABSTRACT: Phase-change materials (PCMs) are a group of chemical compounds that exhibit two stable phases with large contrast in their optical and electrical properties. Moreover, reversible transitions between the two phases can be easily triggered using optical or electrical pulses. These properties make PCMs interesting to implement new applications in photonics. In the first part of the talk we will show an optical switch in a Si ring resonator covered with GST as well as control of surface-plasmon propagation in Au/SiO2 plasmonic waveguides. In the second part we will explain how to combine GST with thin-film multilayer structures, showing how it can be used to tune EOT resonances in periodic arrays of nanoholes drilled in metallic films, achieving large shifts (385 nm) in the resonance wavelength after crystallization. Finally using thin-film interference effects and exploiting the high absorption of GST we demonstrate broadband perfect absorbers in the visible and narrowband absorbers in the NIR.

*Miquel Rude is a graduate student at ICFO
1
May '17
Felix Izrailev  -  Monday, May 1, 2017
The temperature of a single chaotic eigenstate
BUAP, Mexico and Michigan State University
ABSTRACT: The onset of thermalization in a closed system of randomly interacting bosons, at the level of a single eigenstate, is discussed. We focus on the emergence of Bose-Einstein distribution of single-particle occupation numbers and give a local criterion for thermalization. We show how to define the temperature of an eigenstate, provided that it has a chaotic structure in the basis defined by single-particle states. The analytical expression for the eigenstate temperature as a function of the inter-particle interaction and energy is complemented by numerical data. The relation of thermalization to the many-body localization transition is discussed.
6
Sep '17
David Petiteau  -  Wednesday, September 6, 2017
25
Sep '17
Viviana Acquaviva  -  Monday, September 25, 2017
Understanding the Universe through distant galaxies
New York City College of Technology
ABSTRACT: Understanding the physical properties of galaxies and their evolution through cosmic time means learning more about the Hubble expansion, gravity, and the physical mechanisms that regulate the growth of structures. My work focuses on developing and using better tools to extract maximal information from ongoing and future data from large galaxy surveys, such as CANDELS and LSST. I will present my efforts at improving our ability to determine galaxy properties through Spectral Energy Distribution (SED) fitting. I will introduce GalMC and SpeedyMC, the Markov Chain Monte Carlo algorithms for SED fitting I created, and show how they can be used to recover the age, mass, dust content, metallicity and star formation history of galaxies, as well as to jointly determine photometric redshifts and SED fitting parameters. If time allows it, I will describe the science goals of the Hobby Eberly Telescope Dark Energy eXperiment (HETDEX), which is set to discover several hundred thousand Lyman Alpha Emitting galaxies at 2 < z < 3.5 and use them to shed light on the behavior of dark energy and gravity in this largely unexplored redshift range, and summarize our recent efforts in optimizing the sample selection using Bayesian statistics and machine learning techniques.
2
Oct '17
Sarang Gopalakrishnan  -  Monday, October 2, 2017
ABSTRACT: Electronic wave functions in quasiperiodic systems are intermediate between those in crystalline and random systems. Quasiperiodic systems exhibit Anderson localization, but the properties of the localized state and the localization transition are different from those in random systems. We explore various distinctive aspects of localization in quasiperiodic systems, including a multicritical point in quasiperiodic models with power-law hopping and a semimetal-to-metal phase transition in quasiperiodic Dirac materials.
16
Oct '17
Vipin Kerala Varma  -  Monday, October 16, 2017
ABSTRACT: In this talk we report on the response of (quasi)disordered spin-chains to boundary driving through reservoirs at its ends. In the nonequilibrium current-carrying states, anomalous transport rates of spins are shown to be harbored in noninteracting quasidisordered systems at criticality, and far from criticality in the interacting system; in addition, these steady states exhibit spatial fractality in many of its expectation values, opening an alternative route to experimentally probe a system's fractal properties in contrast to measuring quantum wavefunctions.
23
Oct '17
Alexander Granovsky  -  Monday, October 23, 2017
30
Oct '17
Stephen Arnold  -  Monday, October 30, 2017
Opto-mechanics: fabrication of nano and micro-optic sensors
Polytechnic Institute of New York University
8
Nov '17
Daniel Kabat  -  Wednesday, November 8, 2017
13
Nov '17
Michael Mirkin  -  Monday, November 13, 2017
20
Nov '17
Andrew Kent  -  Monday, November 20, 2017
27
Nov '17
Roman Kezerashvili  -  Monday, November 27, 2017
ABSTRACT: A study the formation of a spatially indirect exciton as a pair of an electron and a hole in two layers of gapped graphene, or transition metal dichalcogenide (TMDC), or phosphorene separated by a dielectric is presented. A solution of two-body problem in these systems is discussed. We propose to observe the superfluidity and Bose-Einstein condensation for a quasi-two-dimensional gas of indirect excitons in these quantum heterostructures. The superfluidity of 2D spatially indirect excitons at low densities in TMDC double layers form a two-component weakly interacting gas of A and B excitons. We demonstrate that the mean field critical temperature for a two-component dilute weakly interacting Bose gas of excitons in a TMDC double layer is an increasing function of the factor Q, determined by the effective reduced mass of A and B excitons. We predict that a weakly interacting gas of dipolar excitons in a double layer of phosphorene exhibits superfluidity and show that the critical velocity of superfluidity, the spectrum of collective excitations and mean field critical temperature for superfluidity are anisotropic and depend on the direction of motion of dipolar excitons.
8
Jan '18
Mitsuteru Inoue  -  Monday, January 8, 2018
PDFDownload PDF locationPhysics Conference Room, SB B326 coffee time2:45 pm talk time3:00 pm
ABSTRACT:
The introduction of artificial magnetic structures into magnetic materials can induce novel electromagnetic and spin-wave behavior. Nano- and submicrometer-scale artificial magnetic lattices (AMLs) can control optical (electromagnetic) waves in magnetophotonic crystals [1], volumetric magnetic holograms [2], and labyrinthian magnetic domain structures [3], and can affect spin waves in magnonic crystals [4].
In this talk, the fundamental properties of such AMLs, mainly in magnetic garnet films and alloy thin films, are discussed, followed by demonstrations of their applications in optical and spin-wave micro-devices driven by magnetic phase interference: volumetric magneto-optic (MO) hologram memories [2] and three-dimensional MO holographic displays [5] with magnetophotonic crystals; high-speed MO Q-switch micro-chip lasers with iron-garnet films with labyrinthian magnetic domain structures [3]; and highly sensitive magnetic sensors and spinwave logic circuits with magnonic crystals [6].
Prospective future spin-wave devices with AMLs will be discussed in the context of the new paradigm of magnonics (electron non-transport electronics), where spin waves play an important role as the information carrier.
 
[1] T. Goto et al., “Magnetophotonic crystal comprising electro-optical layer for controlling helicity of light,” J. Appl. Phys., 111, 07A913, 2012.
[2] Y. Nakamura et al., “Error-free reconstruction of magnetic hologram via improvement of recording conditions in collinear optical system,” Optics Exp., 25, 15349-15357, 2017.
[3] R. Morimoto et al., “Magnetic domains driving a Q-switched laser,” Sci. Rep., 6, 38679, 2016.
[4] N. Kanazawa et al., “Metal thickness dependence on spin wave propagation in magnonic .crystal using yttrium iron garnet,” J. Appl. Phys., 117, 17E510, 2015.
[5] K. Nakamura et al., “Improvement of diffraction efficiency of three-dimensional magnetooptic spatial light modulator with magnetophotonic crystal,” Appl. Phys. Lett., 108, 02240, 2016.
[6] N. Kanazawa et al., “Demonstration of a robust magnonic spin wave interferometer,” Sci. Rep., 6. 30268, 2016.
 
NOTES: Professor Inoue is IEEE Magnetics Society Distinguished Lecturer for 2018
29
Jan '18
Mircea Trif  -  Monday, January 29, 2018
ABSTRACT: The field of cavity quantum electrodynamics (cQED) with quantum conductors has become an extremely active field of research. The milestone year was 2004, when superconducting qubits have been integrated within a microwave cavity in order to reach, for the very first time in the condensed matter context, the strong coupling regime between photons and matter [1,2]. Since then, many other systems have been successfully coupled to microwave cavities, such as quantum wires [3], carbon nanotubes [4], quantum dots [5], etc. Such hybrid systems offer platforms for new kinds of physics, as one can engineer and manipulate the electromagnetic environment at will. The versatility of the cQED method relies on the fact that it allows to 1) monitor in a noninvasive fashion the electronic states in quantum conductors, both in equilibrium and non-equilibrium situations, 2) to affect and manipulate the electronic transport, 3) to establish long-range correlations between remote quantum conductors and, finally, 4) it opens the pathway to create non-classical states of light by means of electronic transport.

In this talk, I will discuss some of these aspects for various types of quantum conductors out of equilibrium. I will focus on tunnel junctions [5], magnetic tunnel junctions [6], quantum dots [5] and Josephson junctions [7,8], respectively. I will show that one can reveal properties that are invisible in electronic transport (via the conductance), in particular in out-of-equilibrium situations pertaining to a large voltage bias applied over the quantum conductor [8]. For the case of voltage biased Josephson junction, I will show that the emitted radiation is non-classical in the sense that the photonic correlators violate some Cauchy-Schwarz inequalities [9]. I will confront the theory with some recent experimental studies where such violations have been measured [10].

References:
[1] A. Wallraf, D. I. Schuster, A. Blais et al., Nature 431, 162 (2004).
[2] A. Blais et al., Phys. Rev. A 69, 062320 (2004).
[3] K. D. Petersson et al., Nature 490, 380 (2012). [4] J. Viennot et al., Science 349, 6246 (2015).
[4] T. Frey et al., Phys. Rev. Lett. 108, 046807 (2010).
[5] Olesia Dmytruk, Mircea Trif, Christophe Mora, and Pascal Simon, Phys. Rev. B 93, 075425 (2016).
[6] Mircea Trif and Pascal Simon, Phys. Rev. B 90, 174431 (2014).
[7] Mircea Trif and Pascal Simon, Phys. Rev. B 92, 014503 (2015).
[8] O. Parlavecchio et al, Phys. Rev. Lett. 119, 137001 (2017).  
5
Feb '18
Sateesh Mane  -  Monday, February 5, 2018
Relativistic Spin Polarized Beams in Accelerators
Computer Science, Queens College
ABSTRACT: This talk will present an overview of the subject of relativistic spin polarized beams in particle accelerators. The focus will mainly be high energy accelerators (such as RHIC at Brookhaven National Lab), but lower energy machines for nuclear physics will also be discussed. Highlights such as the precision measurement of the mass of the Z0 boson at CERN will be treated.

http://iopscience.iop.org/article/10.1088/0034-4885/68/9/R01/pdf
26
Feb '18
Aditi Mitra  -  Monday, February 26, 2018
ABSTRACT: Recent advances in ultra-fast measurement in cold atoms, as well as pump-probe spectroscopy of K3C60 films, have opened the possibility of rapidly quenching systems of interacting fermions to, and across, a finite temperature superfluid transition. However determining that a transient state has approached a second-order critical point is difficult, as standard equilibrium techniques are inapplicable. We show that the approach to the superfluid critical point in a transient state may be detected via time-resolved transport measurements, such as the optical conductivity. We leverage the fact that quenching to the vicinity of the critical point produces a highly time dependent density of superfluid fluctuations, which affect the conductivity in two ways. Firstly by inelastic scattering between the fermions and the fluctuations, and secondly by direct conduction through the fluctuations. The competition between these two effects leads to non-monotonic behavior in the time-resolved optical conductivity, providing a signature of the critical transient state
4
Mar '18
Mariangela Lisanti  -  Sunday, March 4, 2018
TBA
Princeton University
5
Mar '18
Donald Weingarten  -  Monday, March 5, 2018
Quantum Mechanics and the Macroscopic World
Indiana University, IBM Research, Finance
19
Mar '18
James Wynne  -  Monday, March 19, 2018
Illuminating My Career: From Flash Gordon to Laser Surgery
IBM Research Laboratory, Yorktown Heights
ABSTRACT:
The ruby laser first "lased" in May, 1960. It was used for retinal surgery in late 1961. Over the next two decades, many laser surgical procedures were developed to remove undesirable tissue or seal bleeding ulcerated tissue, but they all left "therapeutic" scar tissue. 
 
In Nov-Dec, 1981, my IBM colleagues and I discovered that the short pulses of energetic ultraviolet light from an ArF excimer laser, emitting at 193nm (6.4 eV), could produces ultra-clean incisions in animal tissue, in vitro. We conceived that this laser could incise living tissue, which might heal without scarring, because there would be minimal damage to the tissue underlying and adjacent to the incision. Collaboration with ophthalmologists led to the laser refractive surgical procedures known as LASIK and PRK, which have improved the vision of more the 40 million people.
 
In 1983, my colleagues and I discovered that blood absorbed the 6.4 eV light from the ArF excimer laser via a non-thermal process. We thought this meant that we could not use the laser to treat deep skin lesions. 26 years later, in 2009, my dermatologist colleague and I conceived of using the laser as a "smart scalpel" to debride necrotic lesions of the skin, such as burn eschar, leaving the underlying and adjacent viable skin undamaged, resulting in faster healing, less pain, and minimizing scar tissue formation, when compared to "cold steel" debridement. I will report on the latest results of my collaboration with dermatologists at Stony Brook University, where we burn live pigs, debride the necrotic tissue with the ArF excimer laser, and see enhanced healing. Our first peer-reviewed paper, "ArF excimer laser debrides burns without destruction of viable tissue: A pilot study," is In Press, available online, and will be published In Print in the next issue of BURNS.
 
26
Mar '18
ABSTRACT: Recently, BaZr0.2Ti0.8O3 (BZT) based ferroelectric films have exhibited high energy storage densities (up to 166 joules per cubic centimeter) and recycling efficiencies (up to 96 percent). Here, I will introduce you our new investigation of heterophase polydomain structures in BZT films by optical second harmonic generation (SHG) and photo-induced acoustic waves. We analyzed the spatial distribution of SHG intensities and GHz acoustic phonon oscillations. A rhombohedral symmetry is revealed to grow with increasing film thickness as tetragonal domains relax away from the film-substrate interface. The presence of phase segregated tetragonal and rhombohedral structures is further confirmed through TEM and XRD measurements. The high energy performance of the films is explained by ultra-adaptive nanodomains which can effectively accommodate the competing elastic and electrical stress fields during charge-discharge cycles.
 
9
Apr '18
Dimitrios Sounas  -  Monday, April 9, 2018
Nonreciprocal photonics without magnetic biasing
The University of Texas at Austin
ABSTRACT: Reciprocity is a fundamental principle in optics, requiring that the response of a structure is symmetric when source and observation points are interchanged. It is of major significance for the analysis, design and operation of optical systems, but at the same time it poses fundamental limitations on the ways we handle and process optical signals. Nonreciprocal devices, which break this symmetry, have become fundamental in photonic systems for protection of lasers, the separation of signals propagating in opposite directions and the design of photonic topological insulators. Yet, to date they require magnetic materials, making them bulky, costly and unsuitable for integration. This is in stark contrast with most photonic devices, including sources, modulators, switches, waveguides, interconnects and antennas, which may be realized at the nanoscale. In this talk I will show how it is possible to address this problem and design magnetless nonreciprocal devices by using time modulation and nonlinear effects. I will discuss how time modulation allows to impart an effective momentum to a structure and break reciprocity. I will show how this approach can be implemented at different frequency bands, spanning from microwaves to optics. Then, I will present how we can completely remove the requirement of an external bias and realize all-passive nonreciprocal devices by introducing nonlinearities in asymmetric structures. I will discuss fundamental limitations of these devices, stemming from time-reversal symmetry, and show how they can be overcome. I will conclude my talk by providing an outlook for future opportunities of this rapidly advancing research field.
16
Apr '18
Viktoriia Babicheva  -  Monday, April 16, 2018
ABSTRACT: Optical metamaterials are three-dimensional structures with rationally designed building blocks that enable devices with distinct optical responses not attainable with naturally available materials. Comprising a class of metamaterials with a reduced dimensionality, optical metasurfaces allow the miniaturization of conventional refractive optics into planar structures, and a novel planar technology is expected to provide enhanced functionality for photonic devices being distinctly different from those observed in the three-dimensional case. In this talk, I will show that nanostructures made of high-index materials, such as silicon, transition metal dichalcogenides, or hexagonal boron nitride, support optically induced both electric and magnetic resonances in the visible and infrared spectral ranges. I will present the results on antireflective properties of metasurfaces based on high-index nanoparticle arrays and explain how zero backward scattering from the highly reflective substrate can be achieved [1]. Scattering-type scanning near-field optical microscope (s-SNOM) provides optical, chemical, and structural information of metasurfaces and enables their imaging with nanoscale resolution. I will show an approach to analyze layered of materials with different permittivities and demonstrate a technique to identify material type based on near fields at sample edges [2]. The recent discovery of high-index materials that offer low loss and tunability in their optical properties as well as complementary metal-oxide-semiconductor (CMOS) compatibility can enable a breakthrough in the field of nanophotonics, optical metamaterials, and their applications.

[1] V.E. Babicheva and A.B. Evlyukhin, "Resonant Lattice Kerker Effect in Metasurfaces with Electric and Magnetic Optical Responses," Laser & Photonics Reviews 11, 1700132 (2017).
[2] Y. Abate, S. Gamage, L. Zhen, S.B. Cronin, H. Wang, V. Babicheva, M.H. Javani, M.I. Stockman, “Nanoscopy reveals surface-metallic black phosphorus,” Light: Science & Applications 5, e16162 (2016).
 
18
Apr '18
Mohammad Ali Miri  -  Wednesday, April 18, 2018
ABSTRACT: This talk will describe several opportunities for realizing novel nanophotonic devices by employing new degrees of freedom including optical gain and loss as well as mechanical motion. Although most previous efforts on designing photonic devices and structures have been focused on crafting their refractive index profile while avoiding active and dissipative mechanisms, recent investigations suggest the use of such non-conservative processes in order to achieve unusual properties and functionalities. These recent theoretical developments, which are originally inspired by quantum mechanics, have led to the emerging area of non-Hermitian photonics, proposing the conjunctive use of the optical refractive index, gain and loss as three ingredients for photonics design.

In the first part of this talk, I will provide an overview of the fundamental concepts of non-
Hermitian photonics, discuss some of its unique and exotic phenomena and mention potential applications. In particular, I will discuss coupled active/passive resonators and introduce a versatile approach for enforcing single-mode operation in multi-mode laser cavities. The second part of this talk is devoted to micro-/nano-optomechanical cavities as rich platforms for establishing a dynamical coupling between the electromagnetic field and mechanical motion. I will discuss the dynamics of such devices and show that giant optomechanically-induced nonlinear effects, in connection with the optical and mechanical dissipation, offer a viable route for breaking the reciprocity of light in order to realize compact optical isolators and circulators.
23
Apr '18
Xi Chen  -  Monday, April 23, 2018
Evaporation-Driven Engines and Generators
CUNY Advanced Science Research Center
ABSTRACT: Evaporation, which fuels rain and wind, is one of the largest energy flows on Earth. While we can now access many energy sources powered by evaporation, such as hydropower and wind power, the upstream energy of natural evaporation still remains untapped. Water-responsive materials that swell and shrink in response to changes in humidity level can convert evaporation energy into mechanical energy. Bacillus spores are one example of water-responsive materials developed by nature. Our recent study shows that the energy density of spores is significantly higher than all existing actuator materials and artificial muscles. Using spores, we developed two kinds of evaporation-driven engines that can self-start and continuously convert evaporation into mechanical motions, and subsequently into electricity, when placed at air-water interfaces. The energy harvested from evaporation is enough to power a small light source as well as a miniature car.
30
Apr '18
ABSTRACT: Topological phenomena appear in a number of systems, from exotic quantum phases to carefully engineered waveguides. They offer potentially powerful forms of control, and are intriguing in their own right. I will describe a topological feature that is generically present in one of nature's simplest systems: a pair of damped coupled oscillators. I will describe experiments in which we demonstrate this Moebius-strip-like feature and use it to achieve topological control over the excitations in an optomechanical system. I will also describe the nonreciprocal dynamics associated with this feature.
7
May '18
Anthony Pullen  -  Monday, May 7, 2018
ABSTRACT: Emission from ionized carbon, or CII emission, is a promising candidate for tracing the universe through intensity mapping.  In this talk I discuss my latest work, searching for this nearly isotropic CII emission from star-forming galaxies.  After giving an brief introduction to intensity mapping, I will motivate the use of CII intensity mapping  to probe cosmology and galaxy physics.  I will then present the constraints I constructed on CII emission through intensity-galaxy cross-correlations, as well as current research to improve these constraints.  Finally, I will present EXCLAIM, a proposed balloon experiment, of which I am a part, that will aim to map CO and CII emission for studying star formation.
25
Jul '18
Sylvain Gigan  -  Wednesday, July 25, 2018
Optical wave propagation in complex media: from pulse shaping to an invariance of the path length
Sorbonne Université Kastler-Brossel Laboratory, Collège de France
ABSTRACT: Scattering of light in heterogeneous media, for instance the skin or a glass of milk, is usually considered an inevitable perturbation or even a nuisance. Through repeated scattering and interferences, this phenomenon seemingly destroys both the spatial and the phase information of any laser illumination. At the spatial level, it gives rise to the well-known “speckle” interference patterns. At the temporal (or spectral) level, a short pulse entering a scattering medium will see its length greatly extended due to the multiplicity of possible path length light can take before exiting the medium. From an operative point of view, scattering greatly limits the possibility to image or manipulate an object with light through or in a scattering medium. Multiple scattering is nonetheless an invaluable field of research for experimentalists and theoreticians alike, at the crossing of optics, condensed matter physics, statistical physics, chaos, to name just a few. 

Multiple scattering is a highly complex but nonetheless deterministic process: it is therefore reversible, in the absence of absorption. Speckle is coherent, and can be coherently controlled. By « shaping » or « adapting » the incident light, it is in principle possible to control the propagation and overcome the scattering process. I will show our recent results on achieving a complete pulse control (spatial and temporal) by means of wavefront shaping. I will also show the experimental demonstration of a peculiar property of light in disorder, namely that the mean path length is independent of the disorder strength. 
31
Aug '18
Silas Hoffman  -  Friday, August 31, 2018
ABSTRACT: Spin superfluids enable long-distance spin transport through classical ferromagnets by developing topologically protected defects in the magnetic texture. For small spins, in which the magnetization takes quantized values, the topological protection suffers from strong quantum fluctuations. We study the remanence of spin superfluidity inherited from the classical magnet by considering the two-terminal spin transport through a finite spin-1/2 ferromagnetic chain with planar exchange. In the absence of anisotropy in the exchange or an applied magnetic field, the spectrum is gapless. There exist zero-energy domain-wall modes that rotate within the plane of the exchange interaction and are the analogue of the topological defects found in classical magnets. If the system is ordered by an exchange anisotropy, the spectrum is gapped and there exist zero-energy modes localized to the ends of the ferromagnetic chain which are guaranteed by topological properties of the bulk spectrum. We find zero-energy domain-walls, polarized perpendicular to the anisotropy, incident on an ordered chain are reflected as domain-walls polarized in the opposite direction. Furthermore, a domain-wall polarized within the plane of the exchange can be ballistically transmitted through the same magnetic chain of a resonant length. This resonant length depends linearly on the applied magnetic field so that, for a fixed length of chain, the transmission of domain-walls can be tuned by the magnetic field.
17
Sep '18
Misha Sumetsky  -  Monday, September 17, 2018
Localization of light in an optical microcapillary induced by a droplet
Aston University, Institute of Photonic Technologies
ABSTRACT: We show experimentally and theoretically that whispering gallery modes in a silica microcapillary can be fully localized (rather than perturbed) by evanescent coupling to a water droplet and, thus, form a high-quality-factor microresonator. The spectra of this resonator, measured with a microfiber translated along the capillary, present a hierarchy of resonances that allow us to determine the size of the droplet and variation of its length due to the evaporation. The discovered phenomenon of complete localization of light in liquid-filled optical microcapillaries suggests a new type of microfluidic photonic device as well as an ultraprecise method for microfluidic characterization.
24
Sep '18
Alex Krasnok  -  Monday, September 24, 2018
Novel aspects of light scattering
Advance Science Research Center and Graduate Center, CUNY
ABSTRACT: Scattering of electromagnetic waves lies in the heart of the most experimental techniques in radiophysics, visible and X-ray optics that allow us to investigate the micro- and nanoworld. Recently, a wide spectrum of exceptional scattering effects attainable in carefully engineered structures have been predicted and demonstrated. In my talk, I will present our recent results on novel aspects of light scattering including coherent virtual absorption, coherently enhanced WPT, and strong coupling regime in excitonic systems.
15
Oct '18
Larry Liebovitch  -  Monday, October 15, 2018
22
Oct '18
Miriam Rafailovich  -  Monday, October 22, 2018
12
Nov '18
Nikodem Poplawski  -  Monday, November 12, 2018
ABSTRACT: The conservation law for the total (orbital plus spin) angular momentum of a Dirac particle in the presence of gravity requires that spacetime is not only curved, but also has a nonzero torsion. The coupling between the spin and torsion in the Einstein–Cartan theory of gravity generates gravitational repulsion at extremely high densities, which prevents a singularity in a black hole and may create there a new, closed, baby universe undergoing one or more nonsingular bounces. We show that quantum particle production caused by an extremely high curvature near a bounce creates enormous amounts of matter and can generate a finite period of inflation. Our scenario has only one parameter, does not depend significantly on the initial conditions, does not involve hypothetical scalar fields, avoids eternal inflation, and predicts plateau-like inflation that is supported by the Planck observations of the cosmic microwave background. This scenario suggests that our Universe may have originated from a black hole existing in another universe.
26
Nov '18
Ivan Corwin  -  Monday, November 26, 2018
A drunk walk in a drunk world
Columbia University
ABSTRACT: We will consider the effect of a space-time random environment of jumping probabilities on a collection of independent random walkers. Surprisingly, the extreme value behavior for these walkers is governed by the Kardar-Parisi-Zhang universality class which arises in random growth models and random matrix theory. No background of any of these subjects will be assumed.
10
Dec '18
Eleana Makri  -  Monday, December 10, 2018
ABSTRACT: Photonic limiters are protection devices which transmit electromagnetic radiation at low-level incident intensity while blocking high-intensity electromagnetic signals. Passive limiters typically block excessive radiation by means of absorption, which can often cause their destruction due to overheating. We propose the design of a reflective limiter based on resonant transmission through a defect localized mode. The benefit of this design is that it offers protection by reflecting the excessive radiation instead of absorbing it, which reduces overheating problems and results in a device with an extended dynamic range. In this talk, I will present implementations of this idea in band-gap systems in (i) the infrared domain, based on multilayer photonic crystals, and (ii) the microwave domain, based on chiral or CT symmetric coupled resonator waveguide arrays.
17
Dec '18
Andrea Alù  -  Monday, December 17, 2018
New frontiers for light control and manipulation using metamaterials
Advanced Science Research Center and Graduate Center, CUNY
ABSTRACT: Metamaterials are artificial materials with properties well beyond what offered by nature, providing unprecedented opportunities to tailor and enhance the interaction between waves with materials. In this talk, I discuss our recent research activity in electromagnetics, nano-optics and acoustics, showing how suitably tailored meta-atoms and arrangements of them open exciting venues to manipulate and control waves in unprecedented ways. I will discuss our recent theoretical and experimental results, including metamaterials for scattering suppression, metasurfaces to control wave propagation and radiation, large nonreciprocity without magnetic bias, giant nonlinearities in properly tailored metamaterials and metasurfaces, and active metamaterials. Physical insights into these exotic phenomena, new devices based on these concepts, and their impact on technology will be discussed during the talk.
11
Feb '19
Alireza Marandi  -  Monday, February 11, 2019
ABSTRACT: Our life in today’s fast evolving information age is tied to overwhelming technological challenges related to how we capture information on one hand, and, on the other, how we process it. Nonlinear photonic systems are among the growing technologies promising solutions for these challenges by offering paths toward efficient sensing systems for capturing information, and alternative computing platforms for processing it. One example of nonlinear optical processes is half-harmonic generation, which is splitting photons into pairs of photons at half the input frequency that happens in optical parametric oscillators (OPOs) at degeneracy; its intriguing characteristics such as intrinsic phase and frequency locking as well as possibility of generating quantum states of light have opened up unique opportunities for practical and scalable photonic techniques for molecular sensing and non-classical computing.
 
In this talk, I will overview the concept of half-harmonic generation and present the results of realizing efficient sources of femtosecond frequency combs in the mid-infrared based on it [1]. These coherent broadband sources in the molecular fingerprint region of the optical spectrum enable direct sensing of several molecular species simultaneously; a capability that has potential applications in areas such as analysis of greenhouse gases and medical breath analysis.
 
Moreover, I will discuss how half-harmonic generation has enabled development of a novel photonic computing platform, namely the optical Ising machine. Various combinatorial optimization problems in biology, medicine, wireless communications, artificial intelligence and social network that are not easily tractable on conventional computers can be mapped to the Ising problem, and hence the optical Ising machine offers a scalable path for tackling these problems. I will overview a sequence of experiments on development of these half-harmonic-generation-based Ising machines, from their first demonstration in 2014 [2], to a recent large-scale realization that can be programmed to arbitrary Ising problems [3], and one-to-one comparisons with the D-Wave quantum annealer. 
 
I will conclude the talk by presenting our ongoing work on chip-scale implementation of half-harmonic generation and paths toward quantum photonic engineering.
 
References:
[1] A. Marandi et al., Optica 3 (3), 324-327 (2016).
[2] A. Marandi et al., Nature Photonics 8 (12), 937-942 (2014).
[3] P. McMahon*, A. Marandi* et al., Science 354 (6312), 614-617 (2016)
25
Feb '19
Leonardo Ranzani  -  Monday, February 25, 2019
ABSTRACT: Parametric amplifiers increase the measurement fidelity of quantum circuits and are crucial to observe quantum phenomena at microwave as well as optical frequencies. The most common implementation of a lumped-element amplifier is a single nonlinear resonator driven on resonance by a strong electromagnetic pump. In this talk I am going to discuss a more general class of parametric devices consisting of multiple resonant modes coupled via parametric drives. By suitably controlling the amplitude and phases of different parametric processes we can effectively implement new system Hamiltonians, that provide different signal processing functions, such as nonreciprocal signal routing and directional amplification. I will also discuss an implementation of a superconducting multimode parametric circuit on a single chip that can be programmed in situ via a set of microwave drives.
25
Feb '19
David Tannor  -  Monday, February 25, 2019
PDFDownload PDF location309 Remsen Hall
12
Mar '19
Emil Prodan  -  Tuesday, March 12, 2019
18
Mar '19
Mariangela Lisanti  -  Monday, March 18, 2019
Dark matter in disequilibrium
Princeton University
1
Apr '19
Amir Arbabi  -  Monday, April 1, 2019
ABSTRACT: Miniaturized optical systems with planar form factors and low power consumption have many applications in wearable and mobile electronics, health monitoring devices, and as integral parts of medical and industrial equipment. Flat optical devices based on dielectric metasurfaces introduce a new approach for realization of such systems at low cost using conventional nanofabrication techniques. In this talk, I will present our work on dielectric metasurfaces that enable precise control of both polarization and phase with large transmission and high spatial resolution. Optical metasurface components such as MEMs tunable lenses, efficient wave plates, and components with novel functionalities will be discussed. I will also introduce a vertical on-chip integration platform enabled by cascading multiple metasurfaces and active optoelectronic components, and present optical systems such as cameras and spectrometers that have been implemented using this platform. This vertical integration scheme introduces a new architecture for the on-chip integration of conventional optical systems, and enables the unprecedented realization of massively parallel optical systems for computation, data storage, and biomedical sensing applications.
29
Apr '19
Matthew Sfeir  -  Monday, April 29, 2019
Manipulating exciton dynamics for energy conversion applications
Advance Science Research Center and Graduate Center, CUNY
6
May '19
German Kolmakov  -  Monday, May 6, 2019
ABSTRACT: In collaboration with Argonne National Lab (S. Gray, M. Otten, X. Ma), we studied the effects of quantum entanglement in two physical realizations of the excitonic systems: (a) plasmonically coupled quantum dots in an optical cavity and (b) quasi-two-dimensional CdSe/CdS nanoplatelets (NPLs).  Cavity quantum electrodynamics calculations show that upon optical excitation by a femtosecond laser pulse, entanglement of the quantum dot excitons occurs, and the time evolution of the g(2)  pair correlation function of the cavity photons is an indicator of the entanglement. We also show that the degree of entanglement is conserved during the time evolution of the system. Furthermore, if coupling of the photonic cavity and quantum dot modes is large enough, the quantum dot entanglement can be transferred to the cavity modes to increase the overall entanglement lifetime. This latter phenomenon can be viewed as a signature of entangled, long-lived quantum dot exciton-polariton formation. The preservation of total entanglement in the strong coupling limit of the cavity/quantum dot interactions suggests a novel means of entanglement storage and manipulation in high- quality optical cavities. We also find that, due to formation of biexcitons in an NPL and their subsequent decay, the emitted pairs of cavity photons are entangled at temperatures below 20 K. Under favorable conditions the photon pair can be nearly maximally entangled with the relative photon pair population ~0.5. Finally, we discuss possible experiments, in which the NPL generated photon pair entanglement can be observed, as well as potential applications in integrated quantum photonics.
13
May '19
Ana Asenjo-Garcia  -  Monday, May 13, 2019
16
Sep '19
Arkady Plotnitsky  -  Monday, September 16, 2019
ABSTRACT: Bohr never explained what he specifically meant, apart from the fact that complementarity reflects the fundamental difference between quantum physics and classical physics, based on the classical concepts of causality and determinism, closely connected to each other. This talk will introduce the concept of “quantum causality,” which divorces the idea of causality from determinism and explains why one may indeed be see complementarity in this way. This concept, however, is more general and allows one to offer a new perspective on the nature of quantum phenomena and the role of temporality and the arrow of time there, also in connection with quantum information theory, where similar conceptions of causality have been introduced in recent years in the work of C. Brukner, L. Hardy, and G. M. D’Ariano.
23
Sep '19
7
Oct '19
Paul Bourgade  -  Monday, October 7, 2019
ABSTRACT: I will survey properties of eigenstates of large random matrices, both in the Hermitian and non-Hermitian settings. In the Hermitian case, in the past few years universality of eigenvectors statistics (including delocalization) has been established, including for some models with short-range interactions. In the non-Hermitian case, our knowledge is much more limited so we will only consider the "integrable" Ginibre ensemble, exhibiting new statistics for the eigenvectors' overlaps.
21
Oct '19
Volker Sorger  -  Monday, October 21, 2019
ABSTRACT: Photonic technologies are at the forefront of the ongoing 4th industrial revolution of digitalization supporting applications such as virtual reality, autonomous vehicles, and electronic warfare. The development of integrated photonics in recent years enabled functional devices and circuits through miniaturization. However, fundamental challenges such as the weak light-matter integration have limited silicon and III-V-based devices to millimeter-scale footprints demanding about a million photons-per-bit.Overcoming these challenges, in the first part of this talk I will show how nanoscale photonics together with heterogeneous integration of emerging materials into foundry-based photonic chips enables strong nonlinearity, which we use to demonstrate attojoule and compact optoelectronics. Here I will discuss our recent devices demonstrating ITO-based MZI modulators, 2D-material excitonic photodetectors, and exotic epsilon-near-zero modes empowering record-efficient phase shifters for applications in data-comm, LiDAR, and photonic neural networks (NN). Further, I will show that the usually parasitic Kramers-Kronig relations of altering the optical index can be synergistically exploited delivering new modulator operations.

With Moore’s law and Dennard scaling now being limited by fundamental physics, the trend in processor heterogeneity suggests the possibility for special-purpose photonic processors such as NNs or RF-signal & image filtering. Here unique opportunities exist, for example, given by algorithmic parallelism of analog computing enabling non-iterative O(1) processors, thus opening prospects for distributed nonvan Neumann architectures. In the second part of this talk, I will share our latest work on analog photonic processors to include a) a feed-forward fully-connected NN, b) mirror symmetry perception via coincidence detection of spiking NNs, c) a Fourier-optics based convolutional processor with 1 PMAC/s throughputs at nanosecond-short delays for real-time processing, d) a photonic residue arithmetic adder, and e) mesh-based reconfigurable photonic & metatronic PDE solvers. In summary, heterogeneous photonics connects the worlds of electronics and optics, thus enabling new classes of efficient optoelectronics and analog processors by employing the distinctive properties of light.
28
Oct '19
Martin Bojowald  -  Monday, October 28, 2019
ABSTRACT: The big bang is often presented as the beginning of the universe. However, this statement, based on general relativity, follows from an extrapolation of the theory beyond its range of validity because it implies that the density and temperature of matter are infinite at the big bang.  Modern attempts to amend the theory by quantum space-time effects have led to alternative scenarios in which the universe may bounce back after a phase of collapse before the big bang. The physics involved, combining ultra-high density with abstract space-time properties, has not been constrained yet by observational tests, but it is subject to strong conceptual consistency conditions. This talk presents a possible physical picture of the big bang, based on several unexpected properties of space and time in quantum physics.
4
Nov '19
US/Middle East Conference on Photonics  -  Monday, November 4, 2019
Conference
ASRC - The Graduate Center, CUNY
PDFDownload PDF locationASRC Conference Room talk time9:00 am
ABSTRACT: This conference seeks to strengthen engagement between U.S., European, and Middle Eastern scientists by providing a forum for discussion of cutting edge photonics research.


Conference Outline

The conference will take place from Monday-Wednesday, November 4-6 at the Advanced Science Research Center (ASRC) on the campus of City College. Scientific sessions with invited talks will be held over the course of all three days.

On the first night of the conference (Monday, November 4), there will be a reception, early-career scientist symposium, and panel at The Graduate Center, CUNY:

Photonics 3.0: A Worldwide Quest for the Next Technology Revolution

6:30 p.m.

Participants: Nader Engheta (University of Pennsylvania), Mordechai Segev (Technion), and Federico Capasso (Harvard University).
Moderator: Andrea Alù (ASRC/The Graduate Center, CUNY)

Topics covered at the conference include:

› Metamaterials
› Topological insulators
› Biophotonics
› Plasmonics
› Nanooptics
› Integrated photonics
› Quantum optics
› Microwave photonics
› Random media
› Sensing
› Imaging
› Nonlinear optics
› Ultrafast spectroscopy
› Non-Hermitian photonics
11
Nov '19
Morrel Cohen  -  Monday, November 11, 2019
Looking back at seven decades in condensed matter physics
Rutgers University (Physics and Astronomy) and Princeton University (Chemistry and Chemical Biology)
ABSTRACT: I started research in solid state physics in 1950. I have witnessed it evolve into contemporary condensed matter physics over the ensuing seven decades. This talk focusses on several of the key events in the first three of those decades, the ‘50s, ‘60s, and ‘70s, that were fundamental to the emergence of many of the currently exciting areas active today. Being a theorist, I’ll emphasize the theoretical advances. Among those that I’ll of necessity touch on briefly are the introduction of topological reasoning, the growing role of spin-orbit coupling, explaining superconductivity, the discovery of disorder-induced localization, and the evolution of powerful electronic structure computation methods. Looking backward, 1950 was a time of great opportunity. Looking forward, 2019 is a time of even greater opportunity. Condensed matter physics has provided an excellent illustration of Vannevar Bush’s 1945 thesis “Science the Endless Frontier”.
18
Nov '19
Gabriele Grosso  -  Monday, November 18, 2019
2
Dec '19
Amir Ghetmiri  -  Monday, December 2, 2019
Si-based GeSn devices for mid-infrared optoelectronics
University of Arkansas at Pine Bluff
4
Dec '19
Mary Lanzerotti  -  Wednesday, December 4, 2019
PDFDownload PDF locationSB B326 coffee time12:00 pm talk time12:15 pm
ABSTRACT: This talk presents observations of the bursting of thick liquid films of molten steel following illumination of a thin vertical steel plate by a 1075-nm continuous-wave 1000W Ytterbium fiber. Molten steel formed in the illuminated region persists as a molten disk before a hole forms. Gravity is responsible for the formation of a dimple in the upper part of the molten disk and a bulge in the lower part. Images of the initial hole captured by a high-speed digital camera at room temperature conditions show that the hole enlargement is quite sudden, like a soap film popping. Following this, a single drop of molten forms and falls under the influence of gravity below the height of the laser beam, leaving behind a hole in the plate. Images of the initial hole captured by a high-speed digital camera show that the hole forms first in the top portion of the molten disk, not in the center.

The molten steel is modeled as liquid contained within a hoop with size of the final hole. 3D images produced by Surface Evolver, an interactive program for modelling liquid surfaces, indicate the presence of a dimple within the molten region near the location of first appearance of the hole, and a bulge in the molten region near the lower portion for a liquid with density and surface tension taking on values near the melting point of iron.
9
Dec '19
10
Feb '20
Michael Lubell  -  Monday, February 10, 2020
ABSTRACT: Science and the technologies it has spawned have been the principal drivers of the American economy since the end of World War II. Today, economists estimate that a whopping 85 percent of gross domestic product (GDP) growth traces its origin to science and technology. The size of the impact should not be a surprise, considering the ubiquity of modern technologies.

Innovation has brought us the consumer products we take for granted: smart phones and tablets, CD and DVD players, cars that are loaded with electronics and GPS navigating tools and that rarely break down, search engines like Google and Yahoo, the Internet and the Web, money-saving LED lights, microwave ovens and much more. Technology has also made our military stronger and kept our nation safer. It has made food more affordable and plentiful. It has provided medical diagnostic tools, such as MRIs, CT scanners and genomic tests; treatments for disease and illness, such as antibiotics, chemo-therapy, immunotherapy and radiation; minimally-invasive procedures, such as laparoscopy, coronary stent insertion and video-assisted thoracoscopy; and artificial joint and heart valve replacements.

None of those technological developments were birthed miraculously. They owe a significant part of their realization to public and private strategies and public and private investments. Collectively the strategies and investments form the kernel of science and technology policy. Navigating the Maze is a narrative covering more than 230 years of American science and technology history. It contains stories with many unexpected twists and turns, illustrating how we got to where we are today and how we can shape the world of tomorrow.

ABOUT THE SPEAKER

Michael Lubell is the Mark W. Zemansky Professor of Physics at the City College of the City University of New York (CCNY). He has spent much of his career carrying out research in high-energy, nuclear and atomic physics, as well as quantum optics and quantum chaos, and is an elected fellow of the American Association for the Advancement of Science and the American Physical Society He is well known in public policy circles for his ground-breaking work in Washington, DC, where he served as director of public affairs of the American Physical Society for more than two decades. He has published more than 300 articles and abstracts in scientific journals and books and has been a newspaper columnist and opinion contributor for many years. He has been active in local, state and national politics for half a century and has lectured widely in the United States and Europe. Navigating the Maze is his first full-length book.
 
24
Feb '20
ABSTRACT: In this talk, I will discuss the optical biopsy (OB) techniques we have used for cancer diagnosis. Currently the gold-standard method for cancer diagnosis is needle biopsy along with histopathology. This process is invasive, time consuming, and subjective due to the judgment of pathologists. OB is a collection of alternative optical spectroscopy and imaging techniques that are used as diagnostic tools and have attracted enormous attention in the past decades. Native fluorescence spectroscopy (NFS) and Raman spectroscopy (RS) are two important OB techniques which can detect biochemical and morphological information in biological samples at the molecular level based on the excitation, emission, or vibrational properties of the molecules. Such techniques are label free and non-invasive, and can operate rapidly in vivo. We have used these techniques to diagnose different types of cancer, distinguish normal and cancerous tissues, identify cancer grades, detect metastatic ability of cancer cells, etc. 
In particular, I will discuss a new Raman technique, visible resonance Raman (VRR) using 532nm for excitation. Most Raman-based cancer studies in the literature have used near-infrared (NIR) laser excitation, where Raman signal is very weak. Using high power (e.g. 300mW) or long exposure time (e.g. minutes) led to limitation of the technique for practical applications. In contrast, due to the resonance effect, VRR was shown to provide enhanced Raman peaks for key biomolecules which may be used as markers for cancer diagnosis. 
In the meantime, I will discuss the application of artificial intelligence (AI) in the research. Often times, analyzing spectral or imaging data from biological samples is challenging due to the complexity of the data. Machine learning (ML) or deep learning (DL) for AI has been shown to be a promising approach to analyze the “big” data. AI can detect salient features from the high-dimension spectral data, reveal biochemical and morphological information, for accurate diagnosis and prognosis of cells/tissue. 
Optical biopsy with AI techniques brings great opportunities to the field of healthcare. In particular, it provides promising novel techniques for accurate, noninvasive, early detection of cancers.
 
9
Mar '20
ABSTRACT: Our understanding of the universal phenomenon in many-body systems ranging from subatomic to astronomical scales relies largely on the hydrodynamical framework. Thus the discovery of new hydrodynamic effect opens new understanding in a multitude of physical systems.  Such hydrodynamical effect recently has come to fore from Quantum Hall Effect (QHE), where Avron, Seiler, and Zograf showed that the viscosity of QH fluid is purely dissipation-less and is the off-diagonal component of the total viscosity tensor, dubbed `odd' or `Hall' viscosity. It turns out that odd viscosity is not limited to QH, but a special symmetry allowed term of a parity broken system in two dimensions. In this talk, I will outline several fascinating fluid phenomena induced by odd viscosity term such as “odd" torque, “odd" surface waves and  "odd" bubbles and discuss their applicability in a wide class of systems ranging from chiral active matter to fractional quantum Hall effect.
30
Mar '20
Ksenia Dolgaleva  -  Monday, March 30, 2020
TBA
University of Ottawa
6
Apr '20
27
Apr '20
Ricardo Herbonnet  -  Monday, April 27, 2020
4
May '20
Alipasha Vaziri  -  Monday, May 4, 2020
TBA
Rockefeller University