Temperature-dependent carrier-phonon coupling in topological insulator Bi_2Se_3

摘要

Temperature-dependent (11.0 K-294.5 K) carrier-phonon coupling in Bi_2Se_3 is investigated by ultrafast pump-probe spectroscopy. The rise time of the differential reflectivity is interpreted by a combined effect of electron temperature relaxation and hot-phonon lifetime. The electron-phonon coupling constant of the bulk state (λ = 0.63±0.05) is deduced from theoretical fitting. Increasing hot-phonon lifetime with decreasing temperature is attributed to a decreasing phonon-phonon collision rate. A complete analysis of the thermalization process is presented. Understanding carrier and phonon dynamics is essential for future optoelectronic and spintronic applications of topological insulators.