Anderson Localization from Berry-Curvature Interchange in Quantum Anomalous Hall System

TL;DR

This paper explores how the quantum anomalous Hall effect (QAHE) transitions from quantized conductance to an insulating state under increasing disorder, highlighting the role of Berry-curvature interchange in localization.

Contribution

It reveals a disorder-induced phase transition in QAHE driven by Berry-curvature exchange, providing a new understanding of localization mechanisms in topological systems.

Findings

QAHE remains quantized at weak disorder

A metallic phase appears at moderate disorder

Strong disorder leads to Anderson insulating phase

Abstract

We theoretically investigate the localization mechanism of the quantum anomalous Hall effect (QAHE) in the presence of spin-flip disorders. We show that the QAHE keeps quantized at weak disorders, then enters a Berry-curvature mediated metallic phase at moderate disorders, and finally goes into the Anderson insulating phase at strong disorders. From the phase diagram, we find that at the charge neutrality point although the QAHE is most robust against disorders, the corresponding metallic phase is much easier to be localized into the Anderson insulating phase due to the \textit{interchange} of Berry curvatures carried respectively by the conduction and valence bands. At the end, we provide a phenomenological picture related to the topological charges to better understand the underlying physical origin of the QAHE Anderson localization.