Breakdown of ergodicity in disordered U(1) lattice gauge theories

TL;DR

This paper investigates how U(1) lattice gauge theories exhibit ergodicity breaking and quantum chaos breakdown due to Coulomb interactions and random charge backgrounds, with findings robust across system sizes and topological angles.

Contribution

It demonstrates that Coulomb interactions lead to weak finite-volume effects in spectral properties, establishing a clear ergodic-to-nonergodic transition boundary in U(1) lattice gauge theories.

Findings

Spectral properties are weakly affected by finite-volume effects in Coulomb-interacting gauge theories.

A sharp boundary for ergodic regime is identified at accessible system sizes.

Finite-volume effects are stronger in truncated Hilbert space gauge theories, resembling spin chains.

Abstract

We show how U(1) lattice gauge theories display key signatures of ergodicity breaking in the presence of a random charge background. Contrary to the widely studied case of spin models, in the presence of Coulomb interactions, the spectral properties of such lattice gauge theories are very weakly affected by finite-volume effects. This allows to draw a sharp boundary for the ergodic regime, and thus the breakdown of quantum chaos for sufficiently strong gauge couplings, at the system sizes accessible via exact diagonalization. Our conclusions are independent on the value of a background topological angle, and are contrasted with a gauge theory with truncated Hilbert space, where instead we observe very strong finite-volume effects akin to those observed in spin chains.