Ultrafast helicity control of surface currents in topological insulators with near-unity fidelity

TL;DR

This paper demonstrates near-unity fidelity control of surface currents in topological insulators using circularly polarized light on picosecond timescales at room temperature, revealing potential for ultrafast optoelectronic devices.

Contribution

It introduces a method for ultrafast, high-fidelity control of topological insulator surface currents with temporal separation from bulk effects at room temperature.

Findings

Surface currents in Bi2Se3 can be controlled ultrafast with circularly polarized light.

Control fidelity approaches unity even at room temperature.

Temporal separation of surface and bulk currents is achieved.

Abstract

In recent years, a class of solid state materials, called three-dimensional topological insulators, has emerged. In the bulk, a topological insulator behaves like an ordinary insulator with a band gap. At the surface, conducting gapless states exist showing remarkable properties such as helical Dirac dispersion and suppression of backscattering of spin-polarized charge carriers. The characterization and control of the surface states via transport experiments is often hindered by residual bulk contributions yet at cryogenic temperatures. Here, we show that surface currents in Bi2Se3 can be controlled by circularly polarized light on a picosecond time scale with a fidelity near unity even at room temperature. We re-veal the temporal separation of such ultrafast helicity-dependent surface currents from photo-induced thermoelectric and drift currents in the bulk. Our results uncover the functionality of ultrafast optoelectronic devices based on surface currents in topological insulators.