Persistent gapless surface states in MnBi2Te4/Bi2Te3 superlattice antiferromagnetic topological insulator

TL;DR

This study reveals that MnBi4Te7, a superlattice of MnBi2Te4 and Bi2Te3, maintains gapless topological surface states across the antiferromagnetic transition, providing insights into magnetic topological insulators.

Contribution

It demonstrates the persistence of gapless topological surface states in MnBi4Te7 across the AFM transition, advancing understanding of magnetic topological insulators.

Findings

Topological surface states remain gapless across AFM transition.

Bulk bands show strong temperature dependence.

Ubiquitous topological electronic structures identified.

Abstract

Magnetic topological quantum materials (TQMs) provide a fertile ground for the emergence of fascinating topological magneto-electric effects. Recently, the discovery of intrinsic antiferromagnetic (AFM) topological insulator MnBi2Te4 that could realize quantized anomalous Hall effect and axion insulator phase ignited intensive study on this family of TQM compounds. Here, we investigated the AFM compound MnBi4Te7 where Bi2Te3 and MnBi2Te4 layers alternate to form a superlattice. Using spatial- and angle-resolved photoemission spectroscopy, we identified ubiquitous (albeit termination dependent) topological electronic structures from both Bi2Te3 and MnBi2Te4 terminations. Unexpectedly, while the bulk bands show strong temperature dependence correlated with the AFM transition, the topological surface states show little temperature dependence and remain gapless across the AFM transition. The detailed electronic structure of MnBi4Te7 and its temperature evolution, together with the results of its sister compound MnBi2Te4, will not only help understand the exotic properties of this family of magnetic TQMs, but also guide the design for possible applications.