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Conference Paper

Ultrafast far-infrared optics of carbon nanotubes

MPS-Authors
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Frischkorn,  Christian
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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Kampfrath,  Tobias
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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von Volkmann,  Konrad
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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Wolf,  Martin
Physical Chemistry, Fritz Haber Institute, Max Planck Society;

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10.1117_12.pdf
(Any fulltext), 792KB

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Citation

Frischkorn, C., Kampfrath, T., Perfetti, L., von Volkmann, K., & Wolf, M. (2009). Ultrafast far-infrared optics of carbon nanotubes.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0010-FA03-1
Abstract
The optical properties of single-wall carbon nanotube sheets in the far-infrared (FIR) spectral range from few THz to several tens of THz have been investigated with terahertz spectroscopy both with static measurements elucidating the absorption mechanism in the FIR and with time-resolved experiments yielding information on the charge carrier dynamics after optical excitation of the nanotubes. We observe an overall depletion of the dominating broad absorption peak at around 4THz when the nanotubes are excited by a short visible laser pulse. This finding excludes particle-plasmon resonances as absorption mechanism and instead shows that interband transitions in tubes with an energy gap of ~10meV govern the far-infrared conductivity. A simple model based on an ensemble of two-level systems naturally explains the weak temperature dependence of the far-infrared conductivity by the tube-to-tube variation of the chemical potential. Furthermore, the time-resolved measurements do not show any evidence of a distinct free-carrier response which is attributed to the photogeneration of strongly bound excitons in the tubes with large energy gaps. The rapid decay of a featureless background with pronounced dichroism is associated with the increased absorption of spatially localized charge carriers before thermalization is completed.