Metamagnetism of few layer topological antiferromagnets

TL;DR

This study investigates the magnetic phases and topological properties of few-layer MnBi$_2$Te$_4$ using simulations, revealing diverse magnetic configurations and optical responses relevant for topological quantum states.

Contribution

It provides a detailed magnetic phase diagram and optical property analysis for few-layer MnBi$_2$Te$_4$, highlighting the impact of stacking sequences on topological and magneto-optical phenomena.

Findings

Multiple magnetic stacking sequences are possible in MBT.

Certain arrangements exhibit strong Faraday and Kerr effects.

Some configurations have zero Chern number but still show optical responses.

Abstract

MnBi$_2$Te$_4$ (MBT) is a promising antiferromagnetic topological insulator whose films provide access to novel and technologically important topological phases, including quantum anomalous Hall states and axion insulators. MBT device behavior is expected to be sensitive to the various collinear and non-collinear magnetic phases that are accessible in applied magnetic fields. Here, we use classical Monte Carlo simulations and electronic structure models to calculate the ground state magnetic phase diagram as well as topological and optical properties for few layer films with thicknesses up to six septuple layers. Using magnetic interaction parameters appropriate for MBT, we find that it is possible to prepare a variety of different magnetic stacking sequences, some of which have sufficient symmetry to disallow non-reciprocal optical response and Hall transport coefficients. Other stacking arrangements do yield large Faraday and Kerr signals, even when the ground state Chern number vanishes.