Description:

Abstract: It was recently experimentally discovered that magnetically ordered states can persist far from equilibrium – even at energy densities that correspond to infinite temperature. In contrast to their equilibrium –static – counterparts, such states show persistent oscillations of a macroscopic “order parameter.” This phenomenon defies the conventional expectations of thermalization, according to which high energy initial states are supposed to relax very quickly – on a microscopic time scale. It has been proposed that the reason for the observed exotic behavior is the existence of quantum many-body scars (QMBS): atypical many-body eigenstates with low entanglement and sometimes equidistant spectrum. Another mechanism for persistent order parameter oscillations that has been proposed is Continuous Time Crystals – dynamical phases of matter, which, presumably, doe not rely on the very particular eigenstate structure of QMBS. In this talk I will show that both possibilities indeed can be realized within the same clean model. Moreover, even rather strong disorder does not necessarily destroy order parameter oscillations. These observations indicate that quantum many-body systems can evade thermalization and show persistent coherent (oscillatory) dynamics under conditions significantly more generic than previously thought. 

Speaker: Ivar Martin, Argonne National Laboratory 

Host: Ian Mondragon Shem