Spatially resolved femtosecond pump-probe study of topological insulator Bi2Se3

Abstract

Carrier and phonon dynamics in Bi2Se3 crystals are studied by a spatially resolved ultrafast pump-probe technique. Pronounced oscillations in differential reflection are observed with two distinct frequencies, and are attributed to coherent optical and acoustic phonons, respectively. The rising time of the signal indicates that the thermalization and energy relaxation of hot carriers are both sub-ps in this material. We found that the thermalization and relaxation time decreases with the carrier density. The expansion of the differential reflection profile allows us to estimate an ambipolar carrier diffusion coefficient on the order of 500 square centimeters per second. A long-term slow expansion of the profile shows a thermal diffusion coefficient of 1.2 square centimeters per second.

8 pages, 6 figures

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• Effect of carrier recombination on ultrafast carrier dynamics in thin films of the topological insulator Bi2Se3
• Coherent control of injection currents in high-quality films of Bi2Se3
• Clarifying ultrafast carrier dynamics in ultrathin films of the topological insulator Bi2Se3 using transient absorption spectroscopy
• Acoustic phonon dynamics in thin-films of the topological insulator Bi2Se3
• Two-dimensional electronic transport on the surface of 3D topological insulators
• Exciton diffusion in semiconducting single-wall carbon nanotubes studied by transient absorption microscopy
• Observation of antiphase coherent phonons in the warped Dirac cone of Bi${}_2$Te${}_3$
• Surface Optical and Bulk Acoustic Phonons in the Topological Insulator, Bi2Se2Te
• Investigation of structural and magneto-transport properties of PdTe2 single crystals
• Coherent surface-to-bulk vibrational coupling in the 2D topologically trivial insulator Bi2Se3 monitored by ultrafast transient absorption spectroscopy
• Comment on 'Unraveling Photoinduced Spin Dynamics in the Topological Insulator Bi2Se3'
• Two-photon IR pumped UV-Vis transient absorption spectroscopy of Dirac fermions in the 2D and 3D topological insulator Bi2Se3
• Nanosecond dynamics in intrinsic topological insulator ${\text{Bi}}_{2-x}{\text{Sb}}_x{\text{Se}}_3$ revealed by time-resolved optical reflectivity
• Band structure of Bi surfaces formed on Bi2Se3 upon exposure to air
• Tracking the surface atomic motion in a coherent phonon oscillation
• Ultrafast Carrier Relaxation and Second Harmonic Generation in a Higher-Fold Weyl Fermionic System PtAl