Monolayer V2MX4 : A New Family of Quantum Anomalous Hall Insulators

We theoretically propose that the van der Waals layered ternary transition metal chalcogenide V₂MX₄ (M=W, Mo; X=S, Se) is a new family of quantum anomalous Hall insulators with sizable bulk gap and Chern number C=-1. The large topological gap originates from the deep band inversion between spin-up bands contributed by dxz, dyz orbitals of V and spin-down band from d_z² orbital of M at the Fermi level. Remarkably, the Curie temperature of monolayer V₂MX₄ is predicted to be much higher than that of monolayer MnBi₂Te₄. Furthermore, the thickness dependence of the Chern number for few multilayers shows interesting oscillating behavior. The general physics from the d orbitals here applies to a large class of ternary transition metal chalcogenide such as Ti₂WX₄ with the space group P-42m. These interesting predictions, if realized experimentally, could greatly promote the research and application of topological quantum physics.