Quantum anomalous Hall effect in Mn Bi 2 Te 4 van der Waals heterostructures

Quantum anomalous Hall effect (QAHE) has been experimentally realized in the intrinsic antiferromagnetic topological insulator $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$. However, at ambient condition the magnetization of the $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ sample decreases significantly after it is exposed in air for a couple of days, which hinders its potential application. Here, we theoretically propose to cover 2D van der Waals materials such as hexagonal boron nitride (h-BN) monolayer onto the surface of $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$. This not only protects the stability of $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$, but also leads to interlayer ferromagnetic coupling and further realizes the QAHE at higher temperature. We find that interlayer ferromagnetic transition occurs generally when monolayer h-BN, $\mathrm{Mo}{\mathrm{S}}_{2}$, or $\mathrm{W}{\mathrm{Se}}_{2}$ is covered onto two or three septuple-layer $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ with interlayer antiferromagnetic coupling. Band-structure and topological properties calculations show that $\mathrm{h}\ensuremath{-}\mathrm{BN}/\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ heterostructure exhibits a topologically nontrivial band gap around 64--75 meV, hosting QAHE with a Chern number of $C=1$. Our proposed materials system should be considered as an ideal platform to explore high-temperature QAHE due to their relatively simple and stable structures.