Dynamics of many-body localisation in a translation invariant quantum glass model

TL;DR

This study investigates the real-time dynamics of a translation-invariant quantum spin chain, revealing slow relaxation behaviors akin to many-body localisation, driven by initial state fluctuations, with implications for understanding ergodicity breaking.

Contribution

It demonstrates that slow relaxation and MBL-like features can occur in disorder-free quantum systems due to initial state sensitivity, challenging the notion that disorder is essential for MBL.

Findings

Identification of a transition from fast to slow relaxation regimes

Evidence of MBL-like features without disorder in a quantum glass model

Finite size results suggest a possible MBL transition or crossover

Abstract

We study the real-time dynamics of a translationally invariant quantum spin chain, based on the East kinetically constrained glass model, in search for evidence of many-body localisation in the absence of disorder. Numerical simulations indicate a change, controlled by a coupling parameter, from a regime of fast relaxation---corresponding to thermalisation---to a regime of very slow relaxation. This slowly relaxing regime is characterised by dynamical features usually associated with non-ergodicity and many-body localisation (MBL): memory of initial conditions, logarithmic growth of entanglement entropy, and non-exponential decay of time-correlators. We show that slow relaxation is a consequence of sensitivity to spatial fluctuations in the initial state. While numerics indicate that certain relaxation timescales grow markedly with size, our finite size results are consistent both with an MBL transition, expected to only occur in disordered systems, or with a pronounced quasi-MBL crossover.