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Phys. Rev. B 77, 121402(R) (2008) [4 pages]

Ultrafast electron-phonon decoupling in graphite

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Kunie Ishioka*, Muneaki Hase†, and Masahiro Kitajima
Advanced Nano-Characterization Center, National Institute for Materials Science, Tsukuba 305-0047, Japan

Ludger Wirtz
Institute for Electronics, Microelectronics, and Nanotechnology, CNRS, 59652 Villeneuve d’Ascq Cedex, France

Angel Rubio
European Theoretical Spectroscopy Facility, Universidad del País Vasco, Centro Mixto CSIC-UPV/EHU, Edificio Korta, Avenida de Tolosa 72, 20018 Donostia, Spain and Donostia International Physics Center, P. Manuel de Lardizabal 4, 20018 San Sebastian, Spain

Hrvoje Petek
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA and Donostia International Physics Center, P. Manuel de Lardizabal 4, 20018 San Sebastian, Spain

Received 5 December 2007; revised 14 January 2008; published 12 March 2008

We report the ultrafast dynamics of the 47.4 THz coherent phonons of graphite interacting with a photoinduced nonequilibrium electron-hole plasma. Unlike conventional materials, upon photoexcitation the phonon frequency of graphite upshifts, and within a few picoseconds relaxes to the stationary value. Our first-principles density functional calculations demonstrate that the phonon stiffening stems from the light-induced decoupling of the nonadiabatic electron-phonon interaction by creating a nonequilibrium electron-hole plasma. Time-resolved vibrational spectroscopy provides a window on the ultrafast nonquilibrium electron dynamics.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.77.121402
DOI:
10.1103/PhysRevB.77.121402
PACS:
78.47.−p, 63.20.−e, 81.05.Uw

*ishioka.kunie@nims.go.jp

†Present address: Institute of Applied Physics, University of Tsukuba.

 
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