Observation of magnetism induced topological edge state in antiferromagnetic topological insulator MnBi4Te7

TL;DR

This study observes magnetism-induced topological edge states in the antiferromagnetic topological insulator MnBi4Te7, confirming their nontrivial topological nature and dependence on magnetic order through temperature variation.

Contribution

It provides direct experimental evidence of magnetic order influencing topological edge states in MnBi4Te7, a novel antiferromagnetic topological insulator.

Findings

Edge states observed at magnetic MnBi2Te4 layers

Edge states vanish above the Néel temperature

Edge states are absent at non-magnetic layers

Abstract

Breaking time reversal symmetry in a topological insulator may lead to quantum anomalous Hall effect and axion insulator phase. MnBi4Te7 is a recently discovered antiferromagnetic topological insulator with TN ~12.5 K, which is constituted of alternatively stacked magnetic layer (MnBi2Te4) and non-magnetic layer (Bi2Te3). By means of scanning tunneling spectroscopy, we clearly observe the electronic state present at a step edge of a magnetic MnBi2Te4 layer but absent at non-magnetic Bi2Te3 layers at 4.5 K. Furthermore, we find that as the temperature rises above TN, the edge state vanishes, while the point defect induced state persists upon temperature increasing. These results confirm the observation of magnetism induced edge states. Our analysis based on an axion insulator theory reveals that the nontrivial topological nature of the observed edge state.