Topological Magnetic Insulators with Corundum Structure

TL;DR

This paper predicts that corundum-structured transition metal oxides can host strong topological insulator phases and, with electron correlations, can become topological magnetic insulators supporting axionic excitations.

Contribution

It introduces a theoretical model showing corundum-structured oxides can be strong topological insulators and explores their potential to become magnetic topological insulators with axionic states.

Findings

Corundum structure materials can be strong topological insulators.

Electron correlations can induce antiferromagnetic order.

Antiferromagnetic order leads to topological magnetic insulator phase.

Abstract

Topological insulators are new states of quantum matter in which surface states residing in the bulk insulating gap are protected by time-reversal symmetry. When a proper kind of antiferromagnetic long range order is established in a topological insulator, the system supports axionic excitations. In this paper, we study theoretically the electronic states in a transition metal oxide of corundum structure, in which both spin-orbit interaction and electron-electron interaction play crucial roles. A tight-binding model analysis predicts that materials with this structure can be strong topological insulator. Because of the electron correlation, an antiferromagnetic order may develop, giving rise to a topological magnetic insulator phase with axionic excitations.