Quantum anomalous Hall insulator state in ferromagnetically ordered MnBi2Te4/VBi2Te4 heterostructures

The quantum anomalous Hall effect (QAHE) has been experimentally realized in the van der Waals layered topological insulator $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$. However, the antiferromagnetic order of $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ restricts the experimental observation of the QAHE at zero magnetic field. Based on first-principle calculations, we find that stacking $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ with $\mathrm{V}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$, another material from the $\mathrm{M}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ family, can realize a ferromagnetic coupling between layers with an out-of-plane easy axis. The nontrivial topological phase exists in $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}/\mathrm{V}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ bilayers and multilayers. $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ is the main source of QAHE, while $\mathrm{V}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ boosts ferromagnetic coupling between the layers. Thus QAHE can be achieved at zero magnetic field in $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}/\mathrm{V}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ heterostructures, irrespective of odd and even layers. Our finding sheds light on strongly pursuing robust QAHE in van der Waals magnetic topological insulators.