Monolayer V2MX4 : A New Family of Quantum Anomalous Hall Insulators

We theoretically propose that the van der Waals layered ternary transition metal chalcogenide ${\mathrm{V}}_{2}M{X}_{4}$ ($M=\mathrm{W}$, Mo; $X=\mathrm{S}$, Se) is a new family of quantum anomalous Hall insulators with sizable bulk gap and Chern number $\mathcal{C}=\ensuremath{-}1$. The large topological gap originates from the 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 the Fermi level. Remarkably, the Curie temperature of monolayer ${\mathrm{V}}_{2}M{X}_{4}$ is predicted to be much higher than that of monolayer ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$. 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 ${\mathrm{Ti}}_{2}{WX}_{4}$ with the space group $P\text{\ensuremath{-}}42m$. These interesting predictions, if realized experimentally, could greatly promote the research and application of topological quantum physics.