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Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 18: Light-Induced Phenomena

CPP 18.1: Talk

Wednesday, March 28, 2007, 14:30–14:45, H40

Tuning phonon spectra of two-dimensional colloidal crystals — •Jörg Baumgartl1, Maria Zvyagolskaya1, Hans Henning von Grünberg2, and Clemens Bechinger11Universität Stuttgart, 2.Physikalisches Institut, Pfaffenwaldring 57, D-70569 Stuttgart, Germany — 2Karl-Franzens-Universität, Institut für Chemie, Heinrichstraße 28, A-8010 Graz, Austria

By exposing two-dimensional (2D) colloidal crystals to tunable substrate potentials one can selectively manipulate the corresponding phonon band-structure. We explore this idea theoretically and experimentally by studying the overdamped lattice dynamics of colloidal crystals subjected to one- and two-dimensional periodic substrate potentials which are created by interfering laser beams. Experimentally, the phonon spectrum is obtained from the particle dynamics observed by videomicroscopy whereas the theoretical analysis is based on a calculation of the elastic energy of a 2D crystal in the presence of a substrate potential using the harmonic approximation. Depending on the geometry and the strength of the underlying lattice potential, the phonon spectra can be substantially changed which is in agreement with our theoretical calculations.

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