Electronic structures and topological phases of magnetic layered materials MnBi2Te4, MnBi2Se4 and MnSb2Te4

TL;DR

This study uses first-principles calculations to explore the electronic and topological phases of magnetic layered materials MnBi2Te4, MnBi2Se4, and MnSb2Te4, revealing their potential as topological insulators, Weyl semimetals, and Chern insulators under various conditions.

Contribution

It provides a comprehensive analysis of how film thickness, strain, and spin-orbit coupling influence the topological phases of these magnetic layered materials, identifying conditions for Chern insulator states.

Findings

MnBi2Te4 and MnSb2Te4 are AFM topological insulators in bulk form.

MnBi2Se4 remains trivial insulator but can become a topological phase with tuning.

Certain slab thicknesses and strains induce Chern insulator states.

Abstract

First-principles calculations are performed to study the electronic structures and topological phases of magnetic layered materials MnBi2Te4, MnBi2Se4 and MnSb2Te4 under different film thicknesses, strains and spin-orbit coupling (SOC) strengths. All these compounds energetically prefer the antiferromagnetic (AFM) state. MnBi2Te4 and MnSb2Te4 bulks are AFM topological insulators (TIs) in the AFM state, while they become Weyl semimetals in the ferromagnetic (FM) state. MnBi2Se4 is trivially insulating in both the AFM and FM states, but it becomes an AFM TI or a Weyl semimetal with increasing SOC strength or applying compressive strains. Under equilibrium lattice constants, the FM MnBi2Te4 slabs thicker than two septuple layers (SLs), the AFM MnBi2Te4 slabs thicker than three SLs and the FM MnSb2Te4 slabs thicker than five SLs are all Chern insulators. In addition, Chern insulators can also be obtained by compressing the in-plane lattice constants of the FM MnBi2Se4 slabs thicker than four SLs and the FM MnSb2Te4 slabs of three or four SLs, but cannot be obtained using the same method in the AFM slabs of these two materials. In-plane tensile strains about 1% to 2% turn the Chern insulators into trivial insulators.