Robust quantum anomalous Hall effect in graphene-based van der Waals heterostructures

Abstract

The quantum anomalous Hall (QAH) effect is a novel quantum state characterized by edge states which are topologically protected from backscattering and hold great potential for applications in low-power-consumption electronics. The experimental observation of QAH effects in magnetic topological insulators of Cr- or V-doped (Bi,${\mathrm{Sb})}_{2}{\mathrm{Te}}_{3}$ films is, however, full of challenges, hindering seriously the development of this field. Here a robust QAH effect is predicted in a van der Waals (vdW) heterostructure consisting of graphene and a layered ferromagnetic (FM) insulator ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$, from ab initio calculations. The achieved QAH effect is found to be independent of the stacking patterns between graphene and the FM substrate. This robustness makes the experimental observation highly flexible. The Fermi level is found to be located exactly inside the nontrivial bulk band gap which can be tuned effectively by varying the vdW gap. The mechanism is analyzed through tight-binding models. A high Chern number QAH device prototype is proposed, which can dramatically increase the conductance of the device.