Axion Insulator State with ferromagnetic ordering in CrI3/Bi2Se3/MnBi2Se4 Heterostructure

TL;DR

This paper demonstrates the realization of an axion insulator state with uniform magnetization in a heterostructure combining 3D topological insulators and ferromagnetic monolayers, enabling new experimental avenues for topological magnetoelectric effects.

Contribution

It reveals that opposite exchange couplings of magnetic ions in different layers can induce an axion insulator state with uniform magnetization in heterostructures.

Findings

Axion insulator state achieved with uniform magnetization.

Opposite exchange couplings of Cr3+ and Mn2+ ions to surface states.

Potential for exploring topological magnetoelectric effects.

Abstract

Realizing axion insulator state with a uniform magnetization considerably facilitates experimental explorations of the intriguing topological magnetoelectric effect, a hallmark of three-dimensional (3D) topological insulators (TIs). Through density functional theory calculations and four-band model studies, we find that magnetic ions Cr3+ in monolayer CrI3 and Mn2+ in septuple-layer MnBi2Se4 have opposite exchange couplings to the topological surface states of 3D TI Bi2Se3. As an exciting result of such opposite exchange couplings, axion insulator state is realized by a uniform magnetization in CrI3/Bi2Se3/MnBi2Se4 heterostructure. Our work opens up opportunities for exploring topological magnetoelectric effect realized by the uniform magnetization induced axion insulator state in heterostructures of 3D TIs and two-dimensional van der Waals ferromagnetic insulators.