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Soft Matter

Where physics meets chemistry meets biology for fundamental soft matter research.



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Paper

Soft Matter, 2008, 4, 2199 - 2206, DOI: 10.1039/b807881e

Phonon dispersion curves of two-dimensional colloidal crystals: the wavelength-dependence of friction

Jörg Baumgartl, Julian Dietrich, Jure Dobnikar, Clemens Bechinger and Hans Hennig von Grünberg

Digital video-microscopy measurements are reported for both elastic bandstructures and overdamped phonon decay times in two-dimensional colloidal crystals. Both quantities together allow the determination of the friction coefficients along various high symmetry directions in q-space. These coefficients contain valuable information about the hydrodynamics forces acting between the colloidal particles. We find Stokes-like friction for phonons near the edge of the first Brillouin zone and vanishing friction coefficients for long wavelength phonons. The effect of this wavelength-dependence in real-space is further investigated by simulating a crystal with constant friction (Langevin simulation) and comparing experimentally measured and simulated particle auto-correlation functions.

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