# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1902.03372