Ultrafast spin-based devices in topological insulators

Topological insulators (TIs) are becoming a topic of great interest in both fundamental physics and in technological applications, due to their remarkable properties, with an insulating bulk and topologically protected metallic surface states. These surface states exhibit massless Dirac dispersion, as well as locking of spin orientation to the momentum vector, resulting in dissipationless spin currents enabling spintronic devices. We demonstrate efficient linear-optical access to TI Bi2Se3 ultrafast spin dynamics by broadband time-resolved transient reflectivity
measurements.
This enables a practical technique to access spin-current behavior in TI based devices. We exploit the interplay between co- and anti-circular polarizations of the pump and the probe photons at oblique incidence – to distinguish between bulk and surface state responses in optically-excited transitions between two Dirac cones in Bi2Se3 , separated by approximately 1.5 eV