Strain-induced high Chern number topological insulator state in Fe- or V-decorated MoS2 monolayers

The electronic structure and topological state of an ${\mathrm{MoS}}_{2}$ monolayer decorated by iron or vanadium adatoms is investigated by first-principles calculations. It is shown that several Chern insulator phases occur in these samples in the presence of external strain or electric field. In particular, Chern number $\mathcal{C}=2$ is achieved by applying 6% biaxial tensile strain on the V-decorated ${\mathrm{MoS}}_{2}$ monolayer or 10% on the Fe-decorated one. On the other hand, the intrinsic $\mathcal{C}=1$ phase of the iron system is switched to the normal insulator phase under an electric field of 0.8 V/\AA{}, while the vanadium system with intrinsic $\mathcal{C}=\ensuremath{-}1$ state adopts a $\mathcal{C}=1$ state if the electric field reaches 0.7 V/\AA{}. The induced band inversion may coincide with an abrupt increase of magnetization and a simultaneous change in the adatom adsorption height, or a magnetization decrement without displacement of the adatom. Our findings suggest that applying an in-plane biaxial tensile strain is a promising direction to search high Chern number states.