Many-body delocalization with random vector potentials

TL;DR

This paper investigates how random vector potentials affect the localization and ergodic properties of interacting fermions in quasi-one-dimensional chains, revealing that interactions lead to delocalization and ergodicity.

Contribution

It demonstrates that in the presence of interactions, the system becomes ergodic regardless of disorder strength, challenging the standard many-body localization scenario with random gauge fields.

Findings

Noninteracting limit shows localization for any disorder strength.

Interactions induce delocalization and ergodicity.

Localization length diverges with a critical exponent depending on energy density.

Abstract

We study the ergodic properties of excited states in a model of interacting fermions in quasi-one-dimensional chains subjected to a random vector potential. In the noninteracting limit, we show that arbitrarily small values of this complex off-diagonal disorder trigger localization for the whole spectrum; the divergence of the localization length in the single-particle basis is characterized by a critical exponent $\nu$ which depends on the energy density being investigated. When short-range interactions are included, the localization is lost, and the system is ergodic regardless of the magnitude of disorder in finite chains. Our numerical results suggest a delocalization scheme for arbitrary small values of interactions. This finding indicates that the standard scenario of the many-body localization cannot be obtained in a model with random gauge fields.