Electrical Switching of the Edge Current Chirality in Quantum Anomalous Hall Insulators*

A quantum anomalous Hall (QAH) insulator is a topological state of matter, in which the interior is insulating but electrical current flows along the edges of the sample, in either a clockwise (right-handed) or counter-clockwise (left-handed) direction dictated by the spontaneous magnetization orientation. Such chiral edge current (CEC) eliminates any backscattering, giving rise to quantized Hall resistance and zero longitudinal resistance. In this work, we fabricate mesoscopic QAH sandwich (i.e. magnetic topological insulator (TI)/TI/magnetic TI) Hall bar devices and succeed in switching the CEC chirality through spin-orbit torque (SOT) by applying a current pulse under a suitably controlled gate voltage. The well-quantized QAH states before and after SOT switching with opposite CEC chiralities are demonstrated through four- and three-terminal measurements. Our theoretical calculations show that the SOT that enables the magnetization switching can be generated by both bulk and surface carriers in QAH insulators, in good agreement with experimental observations. Finally, I will briefly talk about the SOT switching-induced topological phase transition between the QAH and axion insulator states.