| Abstract: | 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 metalsemiconductor-metal transition upon compression.The resistivity of MnBi_4 Te_7 changes dramatically under high pressure and a non-monotonic evolution of p(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. |
