Ultrafast dynamics of carriers and phonons in topological insulators CuxBi2Se3-y (x=0, 0.1, 0.125, y=0, 1) was studied using femtosecond optical pump-probe spectroscopy. One damped oscillation was clearly observed in the transient reflectivity changes (ΔR/R), which is assigned to the coherent optical phonon (A1g1). According to the red shift of A1g1 phonon frequency, the Cu atoms in CuxBi2Se3 crystals may predominantly intercalated between pair of the quintuple layers. Moreover, the carrier dynamics in the Dirac-cone surface state is significantly different from that in bulk state, which was investigated using optical pump mid-infrared (mid-IR) probe spectroscopy. The rising time and decay time of the negative component in ΔR/R, which is assigned to carrier relaxation in Dirac cone, is 1.62 ps and 20.5 ps, respectively.
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C. W. Luo ; H.-J. Chen ; H. J. Wang ; S. A. Ku ; K. H. Wu, et al.
Ultrafast dynamics in topological insulators
", Proc. SPIE 8623, Ultrafast Phenomena and Nanophotonics XVII, 86230D (March 14, 2013); doi:10.1117/12.2001954; http://dx.doi.org/10.1117/12.2001954