Anomalous helicity-dependent photocurrent in the topological insulator (Bi0.5Sb0.5)2Te3 on a GaAs substrate [Spin manipulation at the interface of a topological insulator and a non-magnetic semiconductor

We present that the emerging material, topological insulator, has provided new opportunities for spintronic applications, owing to its strong spin-orbit character. Topological insulator based heterostructures that display spin-charge coupling driven by topology at surfaces have great potential for the realization of novel spintronic devices. Here, we report the observation of anomalous photogalvanic effect in (Bi_0.5Sb_0.5)₂Te₃ thin films grown on GaAs substrate. We demonstrate that the magnitude, direction, and temperature dependence of the helicity-dependent photocurrent (HDPC) can be modulated by the gate voltage. From spatially resolved photocurrent measurements, we show that the line profile of HDPC in (Bi_0.5Sb_0.5)₂Te₃/GaAs is unaffected by the variation of beam size, in contrast to the photocurrent response measured in a (Bi_0.5Sb_0.5)₂Te₃/mica structure.