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Revealing Optical Transitions and Carrier Recombination Dynamics within the Bulk Band Structure of Bi2Se3
- Publication Year :
- 2018
- Publisher :
- arXiv, 2018.
-
Abstract
- Bismuth selenide (Bi2Se3) is a prototypical three-dimensional topological insulator whose Dirac surface states have been extensively studied theoretically and experimentally. Surprisingly little, however, is known about the energetics and dynamics of electrons and holes within the bulk band structure of the semiconductor. We use mid-infrared femtosecond transient reflectance measurements in a thick exfoliated nanoflake to study the ultrafast thermalization and recombination dynamics of photoexcited electrons and holes within the extended bulk band structure over a wide energy range (0.3-1.2 eV). Theoretical modeling of the reflectivity spectral lineshapes at 10 K demonstrates that the electrons and holes are photoexcited within a dense and cold electron gas with a Fermi level positioned well above the bottom of the lowest conduction band. Direct optical transitions from the first and the second spin-orbit split valence bands to the Fermi level above the lowest conduction band minimum are identified. The photoexcited carriers thermalize rapidly to the lattice temperature within a couple of picoseconds due to optical phonon emission and scattering with the cold electron gas. The minority carrier holes recombine with the dense electron gas within 150 ps at 10 K and 50 ps at 300 K. Such knowledge of interaction of electrons and holes within the bulk band structure provides a foundation for understanding of how such states interact dynamically with the topologically protected Dirac surface states.<br />Comment: 30 pages, 4 figures (Suppl. Info. 8 pages, 3 Tables, 3 Figures)
- Subjects :
- Materials science
Band gap
FOS: Physical sciences
Bioengineering
02 engineering and technology
01 natural sciences
Molecular physics
chemistry.chemical_compound
symbols.namesake
0103 physical sciences
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
General Materials Science
010306 general physics
Electronic band structure
Surface states
Condensed Matter - Mesoscale and Nanoscale Physics
business.industry
Mechanical Engineering
Fermi level
General Chemistry
021001 nanoscience & nanotechnology
Condensed Matter Physics
Semiconductor
chemistry
Topological insulator
symbols
Bismuth selenide
0210 nano-technology
Fermi gas
business
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....d7cefebc930243ff4ebaa3a97b10b523
- Full Text :
- https://doi.org/10.48550/arxiv.1805.09381