Colloquium

Superfluids of Light

Speaker(s): 
David Snoke
Dates: 
Monday, October 14, 2019 - 4:00pm

It is possible to engineer the properties of photons in an optical medium to have an effective mass and repulsive interactions, so that they act like a gas of atoms. These "renormalized photons" are called polaritons. In the past decade, several experiments have demonstrated many of the canonical effects of Bose-Einstein condensation and superfluidity of polaritons. In this talk I will review some of this past work and present recent results with polaritons that have very long lifetime, including movies of equilibration and damped oscillations of a condensate.

From solids with topology to black holes and back

Speaker(s): 
Marcel Franz
Dates: 
Monday, December 2, 2019 - 4:00pm

Inclusion of topological phenomena in condensed matter physics over the past 10 years ushered a new era in this field. As a result of the groundbreaking theoretical insights entire new classes of materials with exotic properties have been discovered, including topological insulators, Dirac and Weyl semimetals as well as topological superconductors containing Majorana fermions. In this talk I will review these developments and discuss an intriguing connection noticed recently by Kitaev between one such topological system – the Sachdev-Ye-Kitaev model – and the horizon of a black hole. This...

Measuring the entropy of a single spin

Speaker(s): 
Joshua Folk
Dates: 
Monday, November 4, 2019 - 4:00pm

Entropy measurements offer a powerful tool for identifying the underlying microscopic character of electronic states.  Such measurements are typically based on bulk properties that are straightforward to observe in macroscopic samples, but exceedingly difficult to access in mesoscopic systems that may consist of just a few electrons or quasiparticles. Taking advantage of a well-known Maxwell relation, we realize a protocol for entropy-to-charge conversation in a gate-defined GaAs quantum dot that enables an entropy measurement of the first three quantum states in the dot. The entropy of a...

Anomalous Velocity and Geometry in Wave Mechanics

Speaker(s): 
Eugene Mele
Dates: 
Monday, October 7, 2019 - 4:00pm

In electronic band theory the dynamics of electrons in crystal lattices can exhibit novel phenomena associated with the anomalous velocity. Modern work on this subject revives an idea which appeared in its primitive form some fifty years ago to interpret the anomalous Hall effect in magnetically ordered states of matter, namely the appearance of a Hall conductivity in materials that have spontaneously broken time reversal symmetry without an applied magnetic field. The signature of the anomalous velocity is the coupling of electron motion to applied static and time-dependent fields through...

SEISMIC: The Sloan Equity and Inclusion in STEM Introductory Courses Project

Speaker(s): 
Tim McKay
Dates: 
Monday, September 23, 2019 - 4:00pm

Equity and inclusion are important goals for higher education. Data can play a central role in achieving these goals. First, data are essential for probing equity. To provide an example, I will describe the discovery of a pattern of gendered performance differences in large foundational courses, both at Michigan and at an array of other Universities. Data can also help create solutions, as when we test new course designs and develop tools that personalize education. 
Over the last year, a group of ten large public research universities have launched the Sloan Equity and Inclusion in...

Faster than fourier (pre)revisited: vorticulture, fractals, escape…

Speaker(s): 
Sir Michael Victor Berry
Dates: 
Monday, September 24, 2018 - 4:30pm to 5:30pm

Band-limited functions can oscillate arbitrarily faster than their fastest Fourier component over arbitrarily long intervals: they can ‘superoscillate’. In physics, this counterintuitive mathematical phenomenon is associated with almost-destructive interference, and occurs near phase singularities in optics and on the world’s ocean tides; and it is associated with quantum weak measurements. Where superoscillations occur, functions are exponentially weak and vulnerable to noise. They are an unexpectedly compact way of representing fractals. Superoscillations in red light can escape as gamma...

Beyond Classical Thermodynamics

Speaker(s): 
Victor Berdichevsky
Dates: 
Monday, April 23, 2018 - 4:30pm to 6:00pm

This colloquium aims to explain why classical thermodynamics is insufficient for solids. After a review of classical equilibrium and non-equilibrium thermodynamics, two examples will be considered, grain growth and crystal plasticity, the latter one in more details. The major complication for development of thermodynamic theory for these cases was the lack of understanding of phase flow geometry. Recently, this geometry was described for dynamics of edge dislocations. Based on this finding, thermodynamics of crystal plasticity can be constructed. It includes two new thermodynamic parameters, entropy and temperature of microstructure.They have simple physical meaning: the rate of microstructure entropy coincides with the rate of slip avalanches while microstructure temperature is average energy drop in a slip avalanche. Perhaps, the phase flow geometry and the corresponding thermodynamic are common for many avalanche-type phenomena.

CASPEr: The lab-scale NMR-based search for axion-like dark matter

Speaker(s): 
Alex Sushkov
Dates: 
Monday, March 26, 2018 - 4:30pm

The nature of dark matter is one of the most important open problems in modern physics. Axions, originally introduced to resolve the strong CP problem in quantum chromodynamics (QCD), and axion-like particles (ALPs) are strongly motivated dark matter candidates. Nuclear spins interacting with axion-like background dark matter experience a torque, oscillating at the axion Compton frequency. The Cosmic Axion Spin Precession Experiments (CASPEr) use precision magnetometry and nuclear magnetic resonance (NMR) techniques to search for the effects of this interaction. CASPEr has the potential to...

How will online learning change the future of STEM courses?

Speaker(s): 
Zhongzhou Chen
Dates: 
Monday, March 12, 2018 - 4:30pm

The concept of “courses ” has not changed much over centuries. However, online learning technology is quickly starting to challenge our understanding of what it means by a “course”. The abundance of online learning resources challenges the role of courses being the disseminators of knowledge, while the high registration numbers and low finishing numbers of Massive Open Online Courses (MOOCs) challenges not only the necessity to “pass” a course, but also the optimum length and scope of a course. Given the fact that more than 70% of today’s undergraduate students are non-traditional in one way or another, it might be a good time to think about how online learning technology might help to evolve the structure of courses to accommodate an increasingly diverse student population. In this workshop, I will initiate the discussion of “what might a future STEM course look like”, by introducing three relatively old ideas: mastery-based learning, flipped or blended classroom , and modularized instructional design. I will talk about how those ideas, when combined with the latest online learning technologies, might re-shape how students take a course, how teachers teach a course, and how instructors create a course , especially for STEM disciplines. We will also brainstorm about what STEM instructors can do to embrace the possible changes ahead.

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