Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
HL: Fachverband Halbleiterphysik
HL 44: Poster Session I
HL 44.9: Poster
Dienstag, 15. März 2011, 18:00–21:00, P3
Phonon dynamics in graphite observed with time-resolved terahertz spectroscopy — •Martin Scheuch1,2, Konrad von Volkmann1,3, Luca Perfetti4, Tobias Kampfrath2, Christian Frischkorn1,2, and Martin Wolf2 — 1Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin — 2Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin — 3APE GmbH Plauener Str. 163-165 Haus N, 13053 Berlin — 4Laboratoire des Solides Irradiés, Ecole polytechnique, 91128 Palaiseau cedex, France
Time-resolved terahertz spectroscopy in the range from 10 to 30 THz is used to monitor the relaxation of highly oriented pyrolytic graphite (HOPG) that has been excited by a laser pulse (wavelength 790 nm, duration 10 fs). The measured pump-induced changes in the complex dielectric function Δε(ω) show that most of the electron excess energy is transferred to few strongly coupled optical phonon modes (SCOPs) on a sub-picosecond timescale. Cooling of the hot SCOPs occurs on a picosecond time scale [1]. Temperature-dependent measurements of the SCOP lifetimes in the range from 10 to 300 K were performed to identify the decay into A′1 and E2g phonons. The results are in agreement with theoretical predictions [2] and show that the A′1 mode at the K point provides the dominant relaxation channel. Additional measurements on naturally grown graphite show no differences to HOPG.
[1] T. Kampfrath et al., Phys. Rev. Lett. 95, 187403 (2005); [2] N. Bonini et al., Phys. Rev. Lett. 99, 176802 (2007)