Anomalous diffusion in colloids confined to quasi-monolayers

Orateur : Martin OETTEL (Eberhard Karls Universitaet Tuebingen Institut fuer Angewandte Physik, Germany)

A colloidal monolayer, e.g., formed at a fluid interface or by means of a suitable confining potential, exhibits anomalous collective diffusion : diffusion becomes accelerated as signalled by a 1/k-divergence of the wavenumber-dependent collective diffusion coefficient. This is a consequence of the hydrodynamic interactions mediated by the three-dimensional (3D) ambient fluid when the particles are confined to reside on a two-dimensional (2D) manifold. We study theoretically and with numerical simulations this phenomenon in strict 2D layers as well as the crossover from normal to anomalous diffusion as the particles are, in real systems, confined by a 3D external potential and thus have the possibility to fluctuate out of the 2D manifold, thus forming a quasimonolayer. In essence, we always find anomalous diffusion on lateral length scales larger than the confinement width.

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