Restoring ergodicity in a strongly disordered interacting chain

TL;DR

This paper demonstrates that a rescaled model of a strongly disordered interacting fermion chain remains ergodic at high disorder levels, challenging the view of many-body localization as a true phase.

Contribution

The authors show that only a small fraction of interactions act as true local perturbations, and by rescaling the model, they restore ergodicity at large disorder.

Findings

True local perturbation decreases with increasing disorder W

Rescaled model remains ergodic even at high W

Strong disorder system behaves as a weakly perturbed integrable model

Abstract

We consider a chain of interacting fermions with random disorder that was intensively studied in the context of many-body localization. We show that only a small fraction of the two-body interaction represents a true local perturbation to the Anderson insulator. While this true perturbation is nonzero at any finite disorder strength W, it decreases with increasing W. This establishes a view that the strongly disordered system should be viewed as a weakly perturbed integrable model, i.e., a weakly perturbed Anderson insulator. As a consequence, the latter can hardly be distinguished from a strictly integrable system in finite-size calculations at large W. We then introduce a rescaled model in which the true perturbation is of the same order of magnitude as the other terms of the Hamiltonian, and show that the system remains ergodic at arbitrary large disorder.