Anomalous helicity-dependent photocurrent in the topological insulator (Bi0.5Sb0.5)2Te3 on a GaAs substrate

The emergingmaterial, topological insulator, has provided newopportunities 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 (Bi0.5Sb0.5)(2)Te-3 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 (Bi0.5Sb0.5)(2)Te-3/GaAs is unaffected by the variation of beam size, in contrast to the photocurrent response measured in a (Bi0.5Sb0.5)(2)Te-3/mica structure.