Pressure-tunable phase transitions in atomically thin Chern insulator MnBi$_2$Te$_4$

TL;DR

This study demonstrates that applying hydrostatic pressure to MnBi$_2$Te$_4$ can tune its magnetic interactions and phase transitions, revealing pressure-dependent topological states and reducing disorder effects in this magnetic topological insulator.

Contribution

It introduces pressure as a tuning parameter to control phase transitions and magnetic interactions in atomically thin MnBi$_2$Te$_4$, a topological insulator with magnetic order.

Findings

Pressure reduces the trivial band gap.

High magnetic field induces a Chern insulator state.

Disorder effects decrease with pressure.

Abstract

Topological insulators lacking time-reversal symmetry can exhibit the quantum anomalous Hall effect. Odd-layer thick MnBi$_2$Te$_4$ is a promising platform due to its intrinsic magnetic nature, however, quantization is rarely observed in it. Our magnetoresistance measurements in the anti-ferromagnetic phase indicate, instead of a quantum anomalous Hall insulator, the presence of a trivial insulator state likely due to disorder, while at high magnetic field a Chern insulator state appears. By applying hydrostatic pressure we are able to tune the magnetic interactions and the characteristic energy scales in the phase diagram. The trivial band gap is reduced, suggesting the role of disorder decreases with the compression of the layers.