Quantum anomalous Hall effect driven by magnetic proximity coupling in all-telluride based heterostructure

The quantum anomalous Hall effect (QAHE) is an exotic quantum phenomenon originating from dissipationless chiral channels at the sample edge. While the QAHE has been observed in magnetically doped topological insulators (TIs), exploiting the magnetic proximity effect on the TI surface from adjacent ferromagnetic layers may provide an alternative approach to the QAHE by opening an exchange gap with less disorder than that in the doped system. Nevertheless, the engineering of a favorable heterointerface that realizes the QAHE based on the magnetic proximity effect remains to be achieved. Here, we report on the observation of the QAHE in a proximity coupled system of a nonmagnetic TI and a ferromagnetic insulator (FMI). We have designed sandwich heterostructures of (Zn,Cr)Te/(Bi,Sb)₂Te₃/(Zn,Cr)Te that fulfills two prerequisites for the emergence of the QAHE: The formation of a sizable exchange gap at the TI surface state and the tuning of the Fermi energy into the exchange gap. The efficient proximity coupling in the all-telluride based heterostructure as demonstrated here will enable a realistic design of versatile tailor-made topological materials coupled with ferromagnetism, ferroelectricity, superconductivity, and so on.