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Berlin 2012 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 5: Soft Matter I

DY 5.9: Topical Talk

Monday, March 26, 2012, 17:00–17:30, MA 004

Phason dynamics in light-induced colloidal quasicrystals — •Michael Schmiedeberg1, Justus Kromer2, and Holger Stark21Institut für Theoretische Physik 2: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Germany — 2Institut für Theoretische Physik, Technische Universität Berlin, Germany

Quasicrystals are non-periodic solids which nevertheless possess long-range positional and orientational order. We study a 2D charge-stabilized colloidal suspension in an external potential with quasicrystalline symmetry. In experiments the potential is realized by five, seven, or more interfering laser beams. A short overview on the properties of light-induced colloidal quasicrystals is presented.

A distinctive physical property of quasicrystals are phasons, which correspond to correlated rearrangements of atoms throughout the quasicrystal. Phasons, like phonons, are hydrodynamic modes since they do not cost free energy in the long-wave-length limit. We perform Brownian dynamics simulations to unravel single-particle dynamics when a constant phasonic drift is applied to the quasicrystalline potential. Single colloids exhibit characteristic trajectories along different directions that are given by their starting positions. Properties of conventional crystals can be deduced from a single unit cell which does not exist in quasicrystals. Nevertheless, we are able to define a characteristic area for phononic and phasonic displacement. We demonstrate that each particle trajectory can then be predicted by mapping it into this area. Our observations help to get a deeper insight into the properties of phasonic displacements in colloidal as well as in atomic quasicrystals.

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