ultraslow dynamics in insulating (Bi,Sb)2Se3

Our new paper is out, “Nanosecond dynamics in intrinsic topological insulator ${\mathrm{Bi}}_{2-x}{\mathrm{Sb}}_x{\mathrm{Se}}_3$ revealed by time-resolved optical reflectivity”

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.L020301

Bi2Se3 is unique among 3D topological insulators (TIs) in its larger bulk band gap, isotropic surface state, and isolated Dirac point, which uniquely lend it to optoelectronic phenomena including exciton condensation.  Optical excitations are made in the bulk, but until now, there has been limited characterization of photoexcited bulk carriers in insulating Bi2Se3 at low temperature.  We show three orders of magnitude slowing of bulk carrier decay rates when Bi2Se3 is made insulating with Sb-doping, and show that the primary relaxation mechanism is via radiative recombination across the bulk band gap, demonstrating previously unreported optical phenomena in a canonical material.