Design of Antiferromagnetic Second-order Band Topology with Rotation Topological Invariants in Two Dimensions

TL;DR

This paper proposes a strategy to realize two-dimensional antiferromagnetic second-order topological insulators with fractional corner charges, using symmetry arguments and first-principles calculations, highlighting potential material candidates like (MnBi2Te4)(Bi2Te3)m.

Contribution

The study introduces a new approach to achieve AFM SOTI phases with in-gap corner states in 2D materials, linking topological invariants to rotation symmetry and identifying realistic material candidates.

Findings

AFM SOTI phases can be realized in (MnBi2Te4)(Bi2Te3)m films.

Corner states are linked to rotation topological invariants under C3 symmetry.

Fractional corner charges quantized to n/3 e are predicted in these systems.

Abstract

The existence of fractionally quantized topological corner states serves as a key indicator for two-dimensional second-order topological insulators (SOTIs), yet has not been experimentally observed in realistic materials. Here, based on effective model analysis and symmetry arguments, we propose a strategy for achieving SOTI phases with in-gap corner states in two dimensional systems with antiferromagnetic (AFM) order. We uncover by a minimum lattice model that the band topology originates from the interplay between intrinsic spin-orbital coupling and interlayer AFM exchange interactions. Using first principles calculations, we show that the 2D AFM SOTI phases can be realized in (MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_{m}$ films. Moreover, we demonstrate that the nontrivial corner states are linked to rotation topological invariants under three-fold rotation symmetry $C_3$, resulting in $C_3$-symmetric SOTIs with corner charges fractionally quantized to $\frac{n}{3} \lvert e \rvert $ (mod $e$). Due to the great recent achievements in (MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_{m}$ systems, our results providing reliable material candidates for experimentally accessible AFM higher-order band topology would draw intense attentions.