Instability of QBC systems to Topological Anderson Insulating phases

TL;DR

This paper investigates how quadratic band crossing systems become unstable and transition into various Chern insulating phases under disorder, revealing emergent gapless phases with topological properties.

Contribution

It introduces a phase diagram showing disorder-induced transitions to novel Chern insulators with C= extpm1, not present in the clean limit.

Findings

Quadratic band crossing points are unstable to disorder, leading to new phases.

Disorder can induce topological Anderson insulators with C= extpm1.

Transitions from trivial to topological phases are driven by disorder.

Abstract

Here we study the instabilities of a quadratic band crossing system to Chern insulating states and uncorrelated disorder. We determined the phase diagram in the plane of topological mass versus disorder strength, characterizing the system with respect to spectral, localization and topological properties. In the clean limit, the system has two gapped Chern insulating phases with Chern numbers C=\pm2, and a trivial phase with C=0. For finite disorder, the quadratic band crossing points are unstable to emergent gapless Chern insulating phases with C=\pm1, not present in the clean limit. These phases occupy a considerable region of the phase diagram for intermediate disorder and show features of topological Anderson insulators: it is possible to reach them through disorder-driven transitions from trivial phases.