Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: POSTER: Biological Systems + New Materials

CPP 20.29: Poster

Wednesday, March 28, 2007, 16:00–18:30, Poster B

Lattice dynamics of a two-dimensional colloidal crystal subjected to a substrate potential — •Maria Zvyagolskaya¹, Jörg Baumgartl¹, Hans Henning von Grünberg², and Clemens Bechinger¹ — ¹Universität Stuttgart, 2.Physikalisches Institut, Pfaffenwaldring 57, D-70569 Stuttgart, Germany — ²Karl-Franzens-Universität, Institut für Chemie, Heinrichstrasse 28, A-8010 Graz, Austria

In the presence of a substrate potential the phonon band-structure of a two-dimensional (2D) crystal can be tuned by varying the strength or the shape of the substrate potential. Here we study this idea by subjecting a 2D colloidal crystal to a commensurate one-dimensional (1D) substrate potential with sinusoidal modulations in one or two spatial directions. Experimental realization of such potentials is achieved by interfering laser beams. We record the trajectories of colloidal particles by means of video-microscopy and then calculate the 1D and 2D phonon band-structure and the phonon spectrum. The 1D band-structure and the phonon spectrum allow for studying how the shape of the band structure is altered by the substrate potential. The 2D band structure displays the breaking of the 6-fold symmetry of the intrinsic colloidal crystal down to a 2-fold symmetry caused by the substrate potential.