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.

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.

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.

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

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 Ba_xSr_1-xTiO₃ films and other members of the Sr_n+1Ti_nO_3n+1 (Ba_n+1Ti_nO_3n+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.

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-T_c 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-T_c cuprates.

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.