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 dz2 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.