Magnetic-field-induced quantized anomalous Hall effect in intrinsic magnetic topological insulator MnBi$_2$Te$_4$

TL;DR

This paper demonstrates that the intrinsic magnetic topological insulator MnBi$_2$Te$_4$ exhibits a quantized anomalous Hall effect when subjected to a magnetic field, providing a disorder-free platform for topological quantum phenomena.

Contribution

It reveals that MnBi$_2$Te$_4$, with intrinsic magnetic order, can show quantized anomalous Hall effect without magnetic doping, unlike previous materials.

Findings

Quantized anomalous Hall response observed in MnBi$_2$Te$_4$ under magnetic field.

Magnetic field induces interlayer ferromagnetic order in the antiferromagnetic crystal.

MnBi$_2$Te$_4$ is the first intrinsic magnetic topological insulator exhibiting this effect.

Abstract

In a magnetic topological insulator, nontrivial band topology conspires with magnetic order to produce exotic states of matter that are best exemplified by quantum anomalous Hall (QAH) insulators and axion insulators. Up till now, such magnetic topological insulators are obtained by doping topological insulators with magnetic atoms. The random magnetic dopants, however, inevitably introduce disorders that hinder further exploration of quantum effects in the material. Here, we resolve this dilemma by probing quantum transport in MnBi$_2$Te$_4$ thin flake - a topological insulator with intrinsic magnetic order. In this layered van der Waals crystal, the ferromagnetic layers couple anti-parallel to each other, so MnBi$_2$Te$_4$ is an antiferromagnet. A magnetic field, however, aligns all the layers and induces an interlayer ferromagnetic order; we show that a quantized anomalous Hall response emerges in atomically thin MnBi$_2$Te$_4$ under a moderate magnetic field. MnBi$_2$Te$_4$ therefore becomes the first intrinsic magnetic topological insulator exhibiting quantized anomalous Hall effect. The result establishes MnBi$_2$Te$_4$ as an ideal arena for further exploring various topological phenomena.