Colloquium

Thermodynamics has shed light on engines, efficiency, and time’s arrow since the Industrial Revolution. But the steam engines that powered the Industrial Revolution were large and classical. Much of today’s technology and experiments are small-scale, quantum, and out-of-equilibrium. Nineteenth-century thermodynamics requires updating for the 21st century. Guidance has come from the mathematical toolkit of quantum information theory. Applying quantum information theory to thermodynamics sheds light on fundamental questions (e.g., how does entanglement spread during quantum thermalization?...

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Novel schemes for optically controlling ferromagnetic order at a femtosecond time scale receive great scientific interest. In the strongly non-equilibrium regime, it has become possible not only to quench magnetic order, but even to deterministically switch the magnetic state by a single femtosecond laser pulses. Moreover, it has been shown that pulsed laser excitation can induce spin currents over several to tens of nanometers. This development triggered a merge of the fields of ‘femto-magnetism’ and spintronics – opening up a fascinating playground for novel physical phenomena. In this...

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Dr. Itamar Kimchi is currently an NRC postdoctoral fellow at JILA, the joint institute of NIST and the Department of Physics at the University of Colorado Boulder

Abstract: Studying quantum entanglement over the past decade has allowed us to make remarkable theoretical progress in understanding correlated many-body quantum systems. However in real materials electrons experience spatially random heterogeneities ("dirt") whose theoretical treatment, including strong correlations, has been a challenge. I will describe how synthesizing ideas from quantum information theory, statistical...

One of the most fascinating aspects of non-equilibrium physics is that a macroscopic quantum system pushed out of equilibrium can exhibit markedly different dynamics when probed on different time scales. Pioneered in time-resolved condensed matter experiments and ultracold atoms, the idea to use external driving such as strong optical pulses holds promise to exceed the limitations set by chemistry and push materials into non-equilibrium states with novel or useful properties. However, a characterization of thermalization, order and dynamics far from equilibrium remains a fundamental...

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.

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...

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...