Pressure-Induced Topological and Structural Phase Transitions in an Antiferromagnetic Topological Insulator*

Recently, natural van der Waals heterostructures of (MnBi 2 Te 4 ) m (Bi 2 Te 3 ) n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states. We systematically investigate both the structural and electronic responses of MnBi 2 Te 4 and MnBi 4 Te 7 to external pressure. In addition to the suppression of antiferromagnetic order, MnBi 2 Te 4 is found to undergo a metal–semiconductor–metal transition upon compression. The resistivity of MnBi 4 Te 7 changes dramatically under high pressure and a non-monotonic evolution of ρ ( T ) is observed. The nontrivial topology is proved to persist 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 MnBi 2 Te 4 , while two high-pressure phase transitions are revealed in MnBi 4 Te 7 . Our combined theoretical and experimental research establishes MnBi 2 Te 4 and MnBi 4 Te 7 as highly tunable magnetic topological insulators, in which phase transitions and new ground states emerge upon compression.