Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 35: Poster Session II (Polymeric biomolecular films; Nanostructures; Electronic structure; Spin-orbit interaction; Phase transitions; Surface chemical reactions; Heterogeneous catalysis; Particles and clusters; Surface magnetism; Electron and spin dynamics; Surface dynamics; Methods; Electronic structure theory; Functional molecules)
O 35.93: Poster
Tuesday, March 27, 2012, 18:15–21:45, Poster B
Nonequilibrium phonon gas in laser-excited solids — •Isabel Klett1, Orkhan Osmani1,2, and Bärbel Rethfeld1 — 1TU Kaiserslautern, 67663 Kaiserslautern, Germany — 2Universität Duisburg-Essen, 47048 Duisburg, Germany
Irradiation of metals with a femtosecond laser pulse leads to a hot electron gas, while the lattice stays nearly cold. Due to the excitation, the electronic system is out of thermal equilibrium, so after laser irradiation, two main processes occur: The first is the electron thermalization, the second is the energy transfer from the electrons to the lattice due to the electron-phonon-coupling. Both processes have been described by assuming a thermalized distribution function for the phononic system. However, due to the fact that only longitudinal phonon modes can absorb the energy of the electrons, this assumption does not hold. Besides, with THz-Lasers [1], different phonon modes can be excited directly, leading to a thermal nonequilibrium within the phononic system. Furthermore, in thin films phonon confinement effects have been observed [2], which is also an indication for a nonequilibrium distribution of the phonons. We describe the phonon-phonon interaction and phonon thermalization with a Boltzmann collision integral. Our aim is to model nonequilibrium phonon distributions and the resulting observable effects after ultrashort laser-matter interaction.
[1] S. Kumar et al., Appl. Phys. Lett. 84, 2494*2496 (2004)
[2] B. Krenzer et al., Phys. Rev B 80, 024307 (2009)