Routes to realize the axion-insulator phase in MnBi$_{2}$Te$_{4}$(Bi$_{2}$Te$_{3}$)$_{n}$ family: a perspective

TL;DR

This paper reviews the conditions, signatures, and recent progress in realizing the axion-insulator phase in MnBi2Te4(Bi2Te3)n family materials, highlighting their potential for topological magnetoelectric effects.

Contribution

It provides a comprehensive perspective on the development, challenges, and experimental evidence related to axion insulators in magnetic topological insulators.

Findings

Discussion of the conditions for axion-insulator phase realization.

Summary of experimental signatures and signatures of axion insulators.

Overview of recent theoretical and experimental advances in the field.

Abstract

Axion, first postulated as a hypothetical particle in high-energy physics, is now extended to describe a novel topological magnetoelectric effect derived from the Chern-Simons theory in condensed matter systems. The recent discovered intrinsic magnetic topological insulators MnBi2Te4 and its derivatives have attracted great attention because of their potential as a material platform to realize such a quantized axion field. Since the magnetic exchange gap can bring the half-quantized anomalous Hall effect at the surface, an axion insulator manifests as quantum anomalous Hall and zero Hall plateau effects in the thin films. However, many puzzles about this material family remain elusive yet, such as the gapless surface state and the direct experimental evidence of the axion insulator. In this Perspective, we discuss the preconditions, manifestations and signatures of the axion-insulator phase, in the context of the development of the natural magnetic topological heterostructure MnBi2Te4(Bi2Te3)n family with various intriguing quantum phenomena. Recent theoretical and experimental efforts regarding the intrinsic magnetic topological insulators are summarized here to pave the way for this phenomenally developing field.