Quantum anomalous Hall effect by coupling heavy atomic layers with CrI3

We explored the possibility of realizing quantum anomalous Hall effect by placing a heavy-element atomic layer on top of monolayer CrI3 with a natural cleavage surface and broken time-reversal symmetry. We showed that CrI3/X (X = Bi, Sb, or As) systems can open up a sizable bulk gap to harbor a quantum anomalous Hall effect; e.g., CrI3/Bi is a natural magnetic insulator with a bulk gap of 30 meV, which can be further enlarged via strain engineering or adjusting spin orientations. We also found that the ferromagnetic properties (magnetic anisotropic energy and Curie temperature) of pristine CrI3 can be further improved due to the presence of heavy atomic layers, and the spin orientation can be utilized as a useful knob to tune the band structure and Fermi level of the CrI3/Bi system. The topological nature, together with the enhanced ferromagnetism, can unlock potential applications for CrI3-based materials in spintronics and electronics.