Temperature-dependent ultrafast carrier and phonon dynamics of topological insulator Bi1.5Sb0.5Te1.8Se1.2

Using ultrafast optical pump-probe technique, we studied the temperature-dependent carrier and phonon dynamics of the topological insulator Bi1.5Sb0.5Te1.8Se1.2 single-crystal from 10K to 300 K. Two relaxation processes of carriers and coherent optical/acoustic phonons have been observed. By using the two-temperature model, we are able to attribute the fast (similar to ps) relaxation component to carrier-phonon coupling involving carriers in the conduction band. We also studied the temperature dependence of the dephasing time and frequency of optical phonon, and the optical penetration depth of Bi1.5Sb0.5Te1.8Se1.2. (C) 2014 AIP Publishing LLC.