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Title: Time-resolved terahertz dynamics in thin films of the topological insulator Bi 2Se 3

We use optical pump–THz probe spectroscopy at low temperatures to study the hot carrier response in thin Bi 2Se 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. Furthermore, 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.
 [1] ;  [2] ;  [3] ;  [3] ;  [2] ;  [2] ;  [3] ;  [2] ;  [2] ;  [2]
  1. The Ohio State Univ., Columbus, OH (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Rutgers the State Univ. of New Jersey, Piscataway, NJ (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0003-6951; APPLAB
Grant/Contract Number:
237789; AC52-06NA25396
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 106; Journal Issue: 1; Journal ID: ISSN 0003-6951
American Institute of Physics (AIP)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
Country of Publication:
United States
36 MATERIALS SCIENCE; ultrafast spectroscopy; topological insulators; surface dynamics; photoexcitations; surface states; surface conductivity; surface photoemission
OSTI Identifier: