Physics (Internal)

Out-of-time-order correlators in disordered quantum systems

This event is part of the Condensed Matter Theory Seminar Series.

Out-of-time-order correlators (OTOC) are used to study the propagation of local information in isolated quantum systems. I will discuss recent results using large scale exact time-evolution for up to L=31 spins 1/2 and show that for weakly disordered nonintegrable systems information propagates behind a ballistically moving front, while the entanglement entropy growths linearly in time. For stronger disorder the motion of the information front is algebraic and sub-ballistic with a disorder strength dependent exponent which depends on the strength of the disorder, similarly to the sublinear growth of the entanglement entropy. The dynamical exponent associated with the information front coincides with the exponent of the growth of the entanglement entropy for both weak and strong disorder and the temporal dependence of the OTOC is characterized by a fast nonexponential growth, followed by a slow saturation after the passage of the information front. Finally, I will mention the implications of this behavioral change on the growth of the entanglement entropy.