Large-Gap Quantum Anomalous Hall effect in a Magnetically doped Type-I Topological Heterostructure

Current method of doping a topological insulator (TI) with magnetic element has only yielded low temperature quantum anomalous hall effect due to the small exchange energy of dopants and uncontrollable shifts in the Fermi-level due to band-bending effects [1]. To overcome the band-bending effect, Fermi -level can be pinned by creating a Type-I type TI/insulator band offset, while the magnetic exchange energy can be increased by searching over different potential magnetic dopants that remain neutral. Given the recent successes of growing high-quality TI-films on Cr₂O₃ heterostructure [2], we study different magnetically doped TI/Cr₂O₃ heterostructures using a combination of density functional theory and k.p modelling. We find Sb₂Te₃ to form a type-I interface with Cr₂O₃l, thereby making the heterostructure insulating, meanwhile maximizing the Zeeman energy due to the segeration of the dopants at the interface, suggesting possible room-temperature QAHE. We also compare our interfacial magnetism model with available experiments.

[1] X. Feng et al, Adv. Mater. 28, 6386 (2016).
[2] F. Wang et al, Nano Lett. 19, 2945 (2019).