Metal-to-Insulator Switching in Quantum Anomalous Hall States

TL;DR

This paper reports the experimental observation of metal-insulator switching in quantum anomalous Hall states, revealing a universal phase diagram and quantum phase transitions with potential applications in quantum physics.

Contribution

It demonstrates the metal-to-insulator transition in QAHE states and maps the universal phase diagram, advancing understanding of quantum phase transitions in topological insulators.

Findings

Giant longitudinal resistance peak observed at coercive field

Zero Hall conductance plateau identified in QAHE

Universal QAHE phase diagram established through angle measurements

Abstract

After decades of searching for the dissipationless transport in the absence of any external magnetic field, quantum anomalous Hall effect (QAHE) was recently achieved in magnetic topological insulator (TI) films. However, the universal phase diagram of QAHE and its relation with quantum Hall effect (QHE) remain to be investigated. Here, we report the experimental observation of the giant longitudinal resistance peak and zero Hall conductance plateau at the coercive field in the 6 quintuple-layer (Cr0.12Bi0.26Sb0.62)2Te3 film, and demonstrate the metal-to-insulator switching between two opposite QAHE plateau states up to 0.3 K. Moreover, the universal QAHE phase diagram is realized through the angle-dependent measurements. Our results address that the quantum phase transitions in both QAHE and QHE regimes are in the same universality class, yet the microscopic details are different. In addition, the realization of the QAHE insulating state unveils new ways to explore quantum phase-related physics and applications.