Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 71: Poster Session: Graphene / Topological Insulators / Interfaces and Surfaces
HL 71.14: Poster
Wednesday, March 28, 2012, 16:00–19:00, Poster D
Ultrafast phonon relaxation in graphite — •Martin Scheuch1, Tobias Kampfrath1, Martin Wolf1, Konrad von Volkmann2, Christian Frischkorn3, and Luca Perfetti4 — 1Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin — 2APE GmbH Plauener Str. 163-165 Haus N, 13053 Berlin — 3Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin — 4Laboratoire des Solides Irradiés, Ecole polytechnique, 91128 Palaiseau cedex, France
A nonequilibrium population of high energy optical phonons (SCOPs) is generated in graphite following the excitation of electron-hole pairs with an 800-nm, 10-fs pump pulse. The energy relaxation of these phonons can be probed by means of time-resolved terahertz spectroscopy of the electronic subsystem because an equilibrium between electrons and SCOPs is established immediately after excitation [1]. To avoid transport effects, measurements are taken on homogenously excited thin films. We find an increase of the hot-phonon lifetime by a factor of two when the sample temperature decreases from 300 K to 5 K. These results suggest that the energy relaxation in graphite is dominated by the anharmonic decay of hot A′1 phonons at the K point into acoustic phonons with energies of about 10 meV [2]. Our results are qualitatively valid for graphene as well [3].
[1] T. Kampfrath et al., Phys. Rev. Lett. 95, 187403 (2005).
[2] M. Scheuch et al., Appl. Phys. Lett. 99, 211908 (2011).
[3] N. Bonini et al., Phys. Rev. Lett. 99, 176802 (2007).