Dynamics and Asymptotics of Correlations in a Many-Body Localized System

TL;DR

This paper investigates how correlations evolve in a disordered quantum spin system, revealing that total correlations better distinguish phases than entanglement, and identifying potential indicators of phase transitions.

Contribution

It demonstrates that total correlations effectively differentiate ergodic and many-body localized phases and suggests their potential as indicators of criticality.

Findings

Concurrence can experience entanglement sudden death and is not always indicative of system properties.

Total correlations reveal fundamental differences between ergodic and localized phases.

Long-time correlation values may indicate the critical region in phase transitions.

Abstract

We examine the dynamics of nearest-neighbor bipartite concurrence and total correlations in the spin-1/2 $XXZ$ model with random fields. We show, starting from factorized random initial states, that the concurrence can suffer entanglement sudden death in the long time limit and therefore may not be a useful indicator of the properties of the system. In contrast, we show that the total correlations capture the dynamics more succinctly, and further reveal a fundamental difference in the dynamics governed by the ergodic versus many-body localized phases, with the latter exhibiting dynamical oscillations. Finally, we consider an initial state composed of several singlet pairs and show that by fixing the correlation properties, while the dynamics do not reveal noticeable differences between the phases, the long-time values of the correlation measures appear to indicate the critical region.