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That is the essence of science: ask an impertinent question, and you are on the way to a pertinent answer.

Jacob Bronowski

Colloquia

Talks start at 12:15 PM
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If not mentioned otherwise, all online Zoom.us events are accessible via this link or use meeting ID 829 2687 2594 and passcode 866995.
4
Oct '21
Next Event
Stanford University
Joseph W. Goodman
Lessons I’ve Learned in Optics: the Roles of Education, Hard Work and Good Luck
Abstract:
This talk draws from lessons I have learned after nearly 60 years of working in optics.  The material presented is aimed at young faculty and students,  describing both my mistakes, disappointments, and what I did right. Regarding education, I review what appear to be common trends in the advancement of technology, and emphasize my view of the type of education that will help one retain relevance during such changes. Regarding hard work, I have found that if you work hard you can overcome many educational shortcomings and, if you enjoy the work you are doing, it doesn’t seem to be hard at all. Finally, regarding good luck, I review the various kinds of good luck that befell me, in hopes that you will find similar good luck in your careers.
18
Oct '21
Vienna University of Technology
Stefan Roter
TBA
25
Oct '21
City College of CUNY
Sriram Ganeshan
TBA
1
Nov '21
The Institute of Optics / University of Rochester
Miguel Alonso
The structure of light: tailoring and measuring intensity, phase and polarization
Abstract:
In this talk I will describe some theoretical aspects of the degrees of freedom of light fields such as amplitude, phase, coherence and polarization. The description of these properties often employs geometric representations that highlight not only their properties but also their analogies with other physical phenomena. I will also present several experimental techniques based on these theoretical methods, for applications such as multicore fiber endoscopes, beam shaping, and superresolution fluorescence microscopy.
15
Nov '21
University of Chicago
Edwin Kite
TBA
22
Nov '21
Queens College of CUNY and Ames Lalboratory
Joshua Aftergood
Developing dynamical probes of quantum spin liquids inspired by techniques from spintronics
Abstract:
This talk is broken into two sections. In the first, we propose an experimental method utilizing a strongly spin-orbit coupled metal-to-quantum magnet bilayer as a probe of quantum magnets lacking long range magnetic order, e.g., quantum spin liquids, via examination of the voltage noise spectrum of the metal layer. The bilayer is held in thermal and chemical equilibrium, and spin fluctuations arising across the interface are converted into voltage fluctuations in the metal as a result of the inverse spin Hall effect. We elucidate the theoretical workings of the bilayer system and provide precise predictions for the frequency characteristics of the enhancement to the ac electrical resistance measured in the metal layer for three candidate quantum spin liquid models. Application to the Heisenberg spin-1/2 kagome lattice model should allow for the extraction of any spinon gap present. A quantum spin liquid consisting of fermionic spinons coupled to a U(1) gauge field should show subdominant Ω^{4/3} frequency scaling of the resistance of the coupled metal. Finally, if the magnet is well-captured by the Kitaev model in the gapless spin liquid phase, then the proposed bilayer can extract the two-flux gap energy which arises in spite of the gapless spectrum of the fermions. We therefore show that spectral analysis of the ac resistance in the metal in a single interface, equilibrium bilayer can test the relevance of quantum spin liquid models to a given candidate material.

In the second section, we examine the temperature dependence of the dc conductivity of a disordered 2d metal when it is interfaced with an insulating paramagnet. The metal contains short-range, isotropic impurities, we consider quantum interference effects, and we include Rashba spin-orbit interactions that arise due to structural inversion symmetry breaking at the interface. The paramagnet acts as a bath of spin fluctuations from the perspective of the metal layer, and the presence of spin fluctuations renormalizes the metallic conductivity. If the affixed insulator is a gapless quantum spin liquid, we show that a lnT correction arises in the absence of spin-orbit interactions while accounting for spin-orbit interactions induces a more divergent T^{-1/2} correction. For temperatures T > T^* ~ 10mK, the lnT correction dominates, whereas for T < T^* the T^{-1/2} correction arising due to spin-orbit interactions takes over. We therefore show that a bilayer as here explicated can act as an all-electrical probe of quantum spin liquid ground states.
 
29
Nov '21
University of Maryland
Rajarshi Roy
Seeing the Light: Photons, Complexity and Randomness
13
Dec '21
University of Science and Technology of Hong Kong
Zhao-Qing Zhang
Anisotropic exceptional points of arbitrary order and some experimental demonstrations