Quantum Anomalous Hall Effect by Coupling Heavy Atomic Layers with CrI${}_3$

Abstract

We explored the possibility of realizing quantum anomalous Hall effect by placing heavy-element atomic layer on top of monolayer CrI${}_3$ with a natural cleavage surface and broken time-reversal symmetry. We showed that CrI${}_3$/X (X = Bi, Sb, or As) systems can open up a sizable bulk gap to harbour quantum anomalous Hall effect, e.g., CrI${}_3$/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 CrI${}_3$ 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 CrI${}_3$/Bi system. The topological nature, together with the enhanced ferromagnetism, can unlock new potential applications for CrI${}_3$-based materials in spintronics and electronics.