Monolayer V2MX4: A new family of quantum anomalous Hall insulators

We theoretically propose that the van der Waals layered ternary transition metal chalcogenide V$_2 MX_4$ ($M=$ W, Mo; $X=$ S, Se) is a new family of quantum anomalous Hall insulators with sizable bulk gap and Chern number $\mathcal{C}=-1$. The large topological gap originates from the \emph{deep} band inversion between spin up bands contributed by $d_{xz},d_{yz}$ orbitals of V and spin down band from $d_{z^2}$ orbital of $M$ at Fermi level. Remarkably, the Curie temperature of monolayer V$_2 MX_4$ is predicted to be much higher than that of monolayer MnBi$_2$Te$_4$. 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 Ti$_2$W$X_4$ with the space group $P$-$42m$. These interesting predictions, if realized experimentally, could greatly promote the research and application of topological quantum physics.