Hannover 2013 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 34: Ultrashort laser pulses: Applications

Q 34.5: Talk

Tuesday, March 19, 2013, 15:00–15:15, F 142

Coherent Phonons in Graphite studied by Femtosecond Transmission Electron Diffraction — •Christian Gerbig, Silvio Morgenstern, Vanessa Sporleder, Cristian Sarpe, Matthias Wollenhaupt, and Thomas Baumert — Universität Kassel, Institut für Physik and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), D-34132 Kassel, Germany

In carbon layered materials (graphite, graphene, carbon nanotubes) the electron subsystem, stimulated by high currents or optical excitations, is strongly coupled to a small set of optical phonons which limits the ballistic conductance. A detailed understanding of phonon decay mechanism is thus essential in improving the performance of carbon-based future electronic devices [1,2]. Time-resolved diffraction, using x-ray or electron probes, has become a promising technique to directly provide insights into dynamics at the molecular level with ultrafast precision [3,4]. We use a femtosecond transmission electron diffractometer to study the evolution of phonon decays in single crystalline graphite after ultrashort laser excitation. Our highly compact setup is well characterized [4] with excellent spatial-temporal resolution (coherence length > 8 nm, electron pulse duration < 200 fs). In this contribution the generation and decay of coherent acoustic phonons are discussed in dependence of film thickness down to few-layer graphene.
[1] T. Kampfrath et al., Phys. Rev. Lett. 95, 187403 (2005)
[2] S. Schäfer et al., New J. Phys. 13, 063030 (2011)
[3] M. Chergui & A. H. Zewail, Chem. Phys. Chem. 10, 28 (2009)
[4] G. Sciaini & R. J. D. Miller, Rep. Prog. Phys 74, 096101 (2011)