Electric control of a canted-antiferromagnetic Chern insulator

TL;DR

This paper demonstrates electrical control of a canted-antiferromagnetic Chern insulator in MnBi2Te4, revealing phase transitions and tunable topological states, advancing potential applications in topological spintronics.

Contribution

It reports the realization of a canted-antiferromagnetic Chern insulator with electrical tunability in MnBi2Te4, a novel system among antiferromagnets.

Findings

Chern insulator state with C=1 appears at the AFM to cAFM transition.

Transition from C=1 to C=2 quantum Hall states observed in magnetic field.

Electrical field can toggle the Chern number on and off near the phase boundary.

Abstract

The interplay between band topology and magnetism can give rise to exotic states of matter. For example, magnetically doped topological insulators can realize a Chern insulator that exhibits quantized Hall resistance at zero magnetic field. While prior works have focused on ferromagnetic systems, little is known about band topology and its manipulation in antiferromagnets. Here, we report that MnBi$_2$Te$_4$ is a rare platform for realizing a canted-antiferromagnetic (cAFM) Chern insulator with electrical control. We show that the Chern insulator state with Chern number $C = 1$ appears as soon as the AFM to canted-AFM phase transition happens. The Chern insulator state is further confirmed by observing the unusual transition of the $C = 1$ state in the cAFM phase to the $C = 2$ orbital quantum Hall states in the magnetic field induced ferromagnetic phase. Near the cAFM-AFM phase boundary, we show that the Chern number can be toggled on and off by applying an electric field alone. We attribute this switching effect to the electrical field tuning of the exchange gap alignment between the top and bottom surfaces. Our work paves the way for future studies on topological cAFM spintronics and facilitates the development of proof-of-concept Chern insulator devices.