Quantum Inverse Freezing and Mirror-Glass Order

TL;DR

This paper demonstrates that mirror-symmetric disorder in an interacting quantum system can induce a finite-energy-density phase with spontaneous mirror symmetry breaking, termed mirror-glass order, enabled by many-body localization and akin to inverse freezing.

Contribution

It introduces the concept of mirror-glass order as a novel form of localization-protected symmetry breaking at finite energy density in quantum systems.

Findings

Mirror-glass order appears at finite energy density.

Mirror-glass transition coincides with localization transition.

The phenomenon is analogous to classical inverse freezing.

Abstract

It is well-known that spontaneous symmetry breaking in one spatial dimension is thermodynamically forbidden at finite energy density. Here we show that mirror-symmetric disorder in an interacting quantum system can invert this paradigm, yielding spontaneous breaking of mirror symmetry only at finite energy density and giving rise to "mirror-glass" order. The mirror-glass transition, which is driven by a finite density of interacting excitations, is enabled by many-body localization, and appears to occur simultaneously with the localization transition. This counterintuitive manifestation of localization-protected order can be viewed as a quantum analog of inverse freezing, a phenomenon that occurs, e.g., in certain models of classical spin glasses.