Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 38: Poster: Colloids and Complex Liquids

CPP 38.17: Poster

Mittwoch, 16. März 2011, 17:00–19:00, P2

Interactions between geometric defects in 2D colloidal systems — •David Polster, Georg Maret, and Peter Keim — Department of Physics, University of Konstanz, D-78464 Konstanz, Germany

Melting in 2D, according to the Kosterlitz-Thouless-Halperin-Nelson-Young theory, involves the formation and dissociation of topological defect pairs. Because these defects distort the hexagonal symmetric of the 2D crystal it is not possible that an isolated topological point defect is formed. Consequently, topological defects occur always as dislocation or disclination pairs.

Geometric defects on the other hand are isolated point defects which can experimentally created e.g. with an optical tweezer. While topological defects appear already near kT geometric defects need a lot more energy to create. We study the interactions of geometric defects with other defects or the surrounding undisturbed lattice in a 2D system of paramagnetic colloidal particles which are sediment to a water/air-interface. By applying a magnetic field the particles form a 2D crystal with hexagonal symmetry which can be manipulated with an optical tweezer. Thereby, we are interested as well in vacancies as in interstitials. First is created by remove a colloidal particle, second by draw a particle into the crystal.