Topological and symmetry-enriched random quantum critical points

TL;DR

This paper investigates how symmetry can enhance disordered quantum critical points, revealing new fixed points with topological edge modes and analyzing their properties using numerical methods.

Contribution

It introduces a new class of symmetry-enriched infinite randomness fixed points with unique boundary and bulk behaviors in disordered quantum spin chains.

Findings

Discovery of symmetry-enriched fixed points with topological edge modes

Bulk properties resemble conventional random singlet phases

Boundary critical behavior governed by distinct fixed points

Abstract

We study how symmetry can enrich strong-randomness quantum critical points and phases, and lead to robust topological edge modes coexisting with critical bulk fluctuations. These are the disordered analogues of gapless topological phases. Using real-space and density matrix renormalization group approaches, we analyze the boundary and bulk critical behavior of such symmetry-enriched random quantum spin chains. We uncover a new class of symmetry-enriched infinite randomness fixed points: while local bulk properties are indistinguishable from conventional random singlet phases, nonlocal observables and boundary critical behavior are controlled by a different renormalization group fixed point. We also illustrate how such new quantum critical points emerge naturally in Floquet systems.