Time-resolved terahertz dynamics in thin films of the topological insulator Bi${}_2$Se${}_3$

Abstract

We use optical pump--THz probe spectroscopy at low temperatures to study the hot carrier response in thin Bi${}_2$Se${}_3$ films of several thicknesses, allowing us to separate the bulk from the surface transient response. We find that for thinner films the photoexcitation changes the transport scattering rate and reduces the THz conductivity, which relaxes within 10 picoseconds (ps). For thicker films, the conductivity increases upon photoexcitation and scales with increasing both the film thickness and the optical fluence, with a decay time of approximately 5 ps as well as a much higher scattering rate. These different dynamics are attributed to the surface and bulk electrons, respectively, and demonstrate that long-lived mobile surface photo-carriers can be accessed independently below certain film thicknesses for possible optoelectronic applications.

arXiv comment4+ pages, 3 figures. Submitted

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Cited by in corpus (14)

• Ultrafast Terahertz Conductivity Probes of Topologically Enhanced Surface Transport Driven by Mid-Infrared Laser Pulses in Bi${}_2$Se${}_3$
• Unraveling photoinduced spin dynamics in topological insulator Bi2Se3
• Observation of Negative THz Photoconductivity in Large Area Type-II Dirac Semimetal PtTe2
• Excitonic Gap Formation in Pumped Dirac Materials
• Revealing Optical Transitions and Carrier Recombination Dynamics within the Bulk Band Structure of Bi2Se3
• Excitonic instability in optically-pumped three-dimensional Dirac materials
• Relaxation dynamics of the optically driven nonequilibrium states in the electron- and hole-doped topological-insulator materials $(B{i}_{1-x}S{b}_x{)}_{2}T{e}_3$
• Nanosecond dynamics in intrinsic topological insulator ${\text{Bi}}_{2-x}{\text{Sb}}_x{\text{Se}}_3$ revealed by time-resolved optical reflectivity
• From classical to quantum regime of topological surface states via defect engineering
• Ultrafast switching of topological invariants by light-driven strain
• Doping-controlled surface conduction in topological insulators with warping effects
• Cyclotron Resonance in Topological Insulators: Non-Relativistic Effects
• Temperature-driven Emergence of Negative Photoconductivity in Semimetal MoTe2 Film Probed with Terahertz Spectroscopy
• Research on topological materials using ultrafast spectroscopy