Ultrafast photocurrents in the topological insulator Sb2Te3 probed by THz emission spectroscopy

The ultrafast photocurrents in a typical 3D topological insulator (TI) Sb2Te3 were probed with THz emission spectroscopy by tuning the polarization of excitation pulses and the sample’s azimuthal angle. The different ultrafast photocurrents driven by the linear photogalvanic effect, circular photogalvanic effect, and thermoelectric effect were distinguished from THz emission signal. Results potentially provide insights into the ultrafast all optical modulation of THz emission with non-external bias field, which could play a vital role in future TI-based high-speed THz optoelectronic and optospintronic devices.