题目：Thermodynamics and order beyond equilibrium -- from Floquet thermalisation to time crystals

报告人：Roderich Moessner   Max Planck Institute for the Physics of Complex Systems

地点： 教十二-201

时间：11月3日，周五，13:30—14:30

摘要：

The field of thermodynamics is one of the crown jewels of classical physics. However, only comparatively recently, due to the advent of experiments in cold atomic systems with long coherence times, has our detailed understanding of its connection to quantum statistical mechanics seen remarkable progress.

Extending these ideas and concepts to the non-equilibrium setting is a challenging topic, in itself of perennial interest. Here, we study perhaps the simplest non-equilibrium class of quantum problems, namely Floquet systems, i.e. systems whose Hamiltonians depend on time periodically,  H(t + T) = H(t). For these, there is no energy conservation, and hence not even a natural concept of temperature.

We find that it is nonetheless possible to identify several fundamentally distinct thermodynamic ensembles.  We also ask if there exists a sharp notion of a phase in such driven, interacting quantum systems. Disorder turns out to play a crucial role, enabling the existence of states which are straightforward analogues of equilibrium states with broken symmetries and topological order, while others--genuinely new to the Floquet problem--are characterized by a combination of order and non-trivial periodic dynamics.

This work was done in collaboration with Arnab Das, Vedika Khemani, Achilleas Lazarides and Shivaji Sondhi.

References:

Phys. Rev. Lett. 112, 150401 (2014);

Phys. Rev. E 90 ,012110 (2014);

Phys. Rev. Lett. 115, 030402 (2015);

Phys. Rev. Lett. 116, 250401 (2016).

个人简介：

Employment 

since 2008          Technical University Dresden, Adjunct Professor for Many-body Physics

since 2007          Max Planck Institute for the Physics of Complex Systems, Dresden, Director

2006 – 2007        Oxford, Theoretical Physics, Somerville College

2001 – 2006        Laboratoire de Physique Théorique, Ecole Normale Supérieure, Paris, and Centre National de la Recherche Scientifique

1998 – 2001        Princeton University, Department of Physics

1997 – 1998        New College, Oxford University

Education  

Graduate student (D.Phil.) in Theoretical Physics, Oxford University   Thesis: Two systems with macroscopically degenerate ground states    Thesis advisor: Prof. J. T. Chalker

B.A. (Honours), Class I in Physics, Oxford University; 1st in class

Scholarships, prizes and distinctions 

Gottfried Wilhelm Leibniz Prize 2013 of the Deutsche Forschungsgemeinschaft

European Physical Society Condensed Matter Division Europhysics Prize 2012

Fellow of the American Physical Society (since 09/15)

Domus Senior Scholar, Merton College, Oxford University

Scott Prize of Oxford University, 1994

Scholar of the German National Scholarship Foundation (Studienstiftung)

Current professional service

Member of the Vorstandsrat of the German Physical Society (until 11/2015)

Divisional Associate Editor, Physical Review Letters

Co-spokesperson of Helmholtz Virtual Institute “New states of matter and their excitations”

欢迎老师和同学参加！