Pressure-induced Topological and Structural Phase Transitions in an Antiferromagnetic Topological Insulator

TL;DR

This study explores how applying pressure to MnBi2Te4 and MnBi4Te7 induces structural and electronic phase transitions, including topological changes, magnetic suppression, and amorphous states, revealing their tunability as magnetic topological insulators.

Contribution

It provides the first systematic investigation of pressure effects on these materials, demonstrating their phase transitions and persistent topological states under high pressure.

Findings

MnBi2Te4 undergoes a metal-semiconductor-metal transition under pressure.

MnBi4Te7 shows dramatic resistivity changes and non-monotonic temperature dependence.

Pressure induces amorphous states in MnBi2Te4 and phase transitions in MnBi4Te7.

Abstract

Recently, natural van der Waals heterostructures of (MnBi2Te4)m(Bi2Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states. In this work, we systematically investigate both the structural and electronic responses of MnBi2Te4 and MnBi4Te7 to external pressure. In addition to the suppression of antiferromagnetic order, MnBi2Te4 is found to undergo a metal-semiconductor-metal transition upon compression. The resistivity of MnBi4Te7 changes dramatically under high pressure and a non-monotonic evolution of \r{ho}(T) is observed. The nontrivial topology is proved to persists before the structural phase transition observed in the high-pressure regime. We find that the bulk and surface states respond differently to pressure, which is consistent with the non-monotonic change of the resistivity. Interestingly, a pressure-induced amorphous state is observed in MnBi2Te4, while two high pressure phase transitions are revealed in MnBi4Te7. Our combined theoretical and experimental research establishes MnBi2Te4 and MnBi4Te7 as highly tunable magnetic topological insulators, in which phase transitions and new ground states emerge upon compression.