Helicity-dependent photocurrent of topological surface states in the intrinsic magnetic topological insulator MnBi2Te4

Helicity-dependent photocurrent (HDPC) of the topological surface states (TSSs) in the intrinsic magnetic topological insulator MnBi2Te4 is investigated. It is revealed that the HDPC is mainly contributed by the circular photogalvanic effect (CPGE) current when the incident plane is perpendicular to the connection of the two electrodes, while the circular photon drag effect plays the dominant role when the incident plane is parallel to the connection of the two electrodes. The CPGE current shows an odd function dependence on incident angles, which is consistent with the C 3 v symmetry group of the TSSs in MnBi2Te4. The amplitude of the CPGE current increases with the decrease in temperature, which can be attributed to the increase in mobility at low temperatures, confirmed by the transport measurements. Furthermore, we modulate the CPGE of MnBi2Te4 by applying top gate and source-drain voltages. Compared to Bi2Te3 of the same thickness, the CPGE current of MnBi2Te4 can be more effectively tuned by the top gate because the Fermi level of MnBi2Te4 can be effectively regulated by the top gate, and it is tuned across the Dirac point. This work suggests that the intrinsic magnetic topological insulator MnBi2Te4 is a good candidate for designing opto-spintronics devices.