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Ultrafast Spectral Photoresponse of Bilayer Graphene: Optical Pump–Terahertz Probe Spectroscopy

Photoinduced terahertz conductivity Δσ(ω) of Bernal stacked bilayer graphene (BLG) with different dopings is measured by time-resolved optical pump terahertz probe spectroscopy. The real part of photoconductivity Δσ(ω) (ΔσRe(ω)) is positive throughout the spectral range 0.5–2.5 THz in low-doped BLG. This is in sharp contrast to Δσ(ω) for high-doped bilayer graphene where ΔσRe(ω) is negative at low frequency and positive on the high frequency side. We use Boltzmann transport theory to understand quantitatively the frequency dependence of Δσ(ω), demanding the energy dependence of different scattering rates such as short-range impurity scattering, Coulomb scattering, carrier–acoustic phonon scattering, and substrate surface optical phonon scattering. We find that the short-range disorder scattering dominates over other processes. The calculated photoconductivity captures very well the experimental conductivity spectra as a function of lattice temperature varying from 300 to 4 K, without any empirical fitting...

Authors:   Srabani Kar; Van Luan Nguyen; Dipti R. Mohapatra; Young Hee Lee; A. K. Sood
Journal:   ACS Nano
Year:   2018
DOI:   10.1021/acsnano.7b08555
Publication date:   18-Jan-2018
Facts, background information, dossiers
  • Energy
  • disorder
  • dependence
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