Domain Formation Driven by the Entropy of Topological Edge Modes

TL;DR

This paper investigates how the entropy of topological edge modes influences phase transitions in systems with spontaneous discrete symmetry breaking, revealing a disorder-driven transition between uniform and domain-structured phases.

Contribution

It introduces a novel mechanism where edge mode entropy induces a thermal transition, supported by a phenomenological model and a microscopic example, with potential experimental realization in graphene-based heterostructures.

Findings

Edge mode entropy drives a phase transition.

Disorder induces domain formation at the edges.

Proposed experimental detection in moiré heterostructures.

Abstract

In this Letter we study interacting systems with spontaneous discrete symmetry breaking, where the degenerate symmetry-broken states are topologically distinct gapped phases. Edge modes appear at domain walls between the two topological phases. In the presence of a weak disorder field conjugate to the order parameter, we find that the entropy of the edge modes drives a thermal transition between a gapped uniform phase and a phase with a disorder-induced domain structure. We characterize this transition using a phenomenological Landau functional, and corroborate our conclusions with a concrete microscopic model. Finally, we discuss the possibilities of experimental signatures of this phase transition, and propose graphene-based moir\'e heterostructures as candidate materials in which such a phase transition can be detected.