TY - GEN
T1 - Ultrafast changes in the far-infrared conductivity of carbon nanotubes
AU - Frischkorn, C.
AU - Kampfrath, T.
AU - Von Volkmann, K.
AU - Perfetti, L.
AU - Wolf, M.
PY - 2008/12/31
Y1 - 2008/12/31
N2 - The ultrafast charge-carrier dynamics in single-wall carbon nanotubes (NTs) have been investigated by time-resolved THz spectroscopy. Both the equilibrium and non-equilibrium conductivity data of the NTs in the far-infrared (FIR) spectral range from 1 to 40 THz are dominated by optical transitions across the band gap of tubes with gap energies of ∼ 10 meV. A simple model based on an ensemble of two-level systems excellently explains all experimental findings. In particular, the surprisingly weak temperature dependence of the FIR conductivity has been shown to arise from tube-to-tube variation of the chemical potential which is ∼ 100 meV in our sample. The results strongly suggest to use the temperature dependence of the FIR conductivity as a very sensitive and contact-free probe of the NT sample purity. Finally, the relaxation of the photo-excited NT sheet on a picosecond time scale mainly reflects the cooling of hot phonons which is about five times faster than in graphite. This points to much stronger lattice anharmonicities in NTs.
AB - The ultrafast charge-carrier dynamics in single-wall carbon nanotubes (NTs) have been investigated by time-resolved THz spectroscopy. Both the equilibrium and non-equilibrium conductivity data of the NTs in the far-infrared (FIR) spectral range from 1 to 40 THz are dominated by optical transitions across the band gap of tubes with gap energies of ∼ 10 meV. A simple model based on an ensemble of two-level systems excellently explains all experimental findings. In particular, the surprisingly weak temperature dependence of the FIR conductivity has been shown to arise from tube-to-tube variation of the chemical potential which is ∼ 100 meV in our sample. The results strongly suggest to use the temperature dependence of the FIR conductivity as a very sensitive and contact-free probe of the NT sample purity. Finally, the relaxation of the photo-excited NT sheet on a picosecond time scale mainly reflects the cooling of hot phonons which is about five times faster than in graphite. This points to much stronger lattice anharmonicities in NTs.
UR - https://www.scopus.com/pages/publications/58049099480
U2 - 10.1109/ICIMW.2008.4665509
DO - 10.1109/ICIMW.2008.4665509
M3 - Conference contribution
AN - SCOPUS:58049099480
SN - 9781424421206
T3 - 33rd International Conference on Infrared and Millimeter Waves and the 16th International Conference on Terahertz Electronics, 2008, IRMMW-THz 2008
BT - 33rd International Conference on Infrared and Millimeter Waves and the 16th International Conference on Terahertz Electronics, 2008, IRMMW-THz 2008
T2 - 33rd International Conference on Infrared and Millimeter Waves and the 16th International Conference on Terahertz Electronics, 2008, IRMMW-THz 2008
Y2 - 15 September 2008 through 19 September 2008
ER -