Polarization-controlled picosecond currents in topological insulators

Controlling spin currents in topological insulators may lead to applications in future spintronic devices [1]. Here, we show that surface currents in Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ can be controlled by circularly polarized light on a time-scale of a picosecond with a fidelity near unity even at room temperature. We reveal the temporal interplay of such ultrafast spin currents with photo-induced thermoelectric and drift currents in optoelectronic circuits [2]. [1] C. Kastl, et al, APL 101, 251110 (2012). [2] C. Kastl et al. under review (2013).