Electric field induced topological phase transition and large enhancements of spin-orbit coupling and Curie temperature in two-dimensional ferromagnetic semiconductors

摘要

Tuning the topological and magnetic properties of materials by applying an electric field is widely used in spintronics. In this work, we find a topological phase transition from topologically trivial to nontrivial states at an external electric field of about 0.1 V/A in a MnBi_2Te_4 monolayer that is a topologically trivial ferromagnetic semiconductor. It is shown that when electric field increases from 0 to 0.15 V/A, the magnetic anisotropy energy (MAE) increases from about 0.1 to 6.3 meV, and the Curie temperature T_C increases from 13 to about 61 K. The increased MAE mainly comes from the enhanced spin-orbit coupling due to the applied electric field. The enhanced T_C can be understood from the enhanced p-d hybridization and decreased energy difference between p orbitals of Te atoms and d orbitals of Mn atoms. Moreover, we propose two Janus materials. MnBi_2Se_2Te_2 and MnBi_2S_2Te_2 monolayers with different internal electric polarizations, which can realize the quantum anomalous Hall effect (QAHE) with Chern numbers C = 1 and C = 2, respectively. Our study not only exposes the electric field induced exotic properties of the MnBi_2Te_4 monolayer but also proposes materials to realize QAHE in ferromagnetic Janus semiconductors with electric polarization.