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DY: Fachverband Dynamik und Statistische Physik

DY 27: Statistical Physics: Far From Equilibrium I

DY 27.3: Vortrag

Mittwoch, 29. März 2023, 10:15–10:30, ZEU 250

Colloidal monolayers: bridging the gap between two and three spatial dimensions — Johannes Bleibel², •Alvaro Domínguez¹, and Martin Oettel² — ¹Univ. Sevilla, Spain — ²Univ. Tübingen

It is well established that, unlike for a three-dimensional fluid, particle interactions prevent the hydrodynamic transport coefficients from being defined for a two-dimensional fluid due to the notorious “long-time tail” feature of the velocity autocorrelation.

A colloidal monolayer formed at a fluid interface builds a bridge between these two limiting cases, and it provides insight on the transition from three down to two spatial dimensions: the particle positions are constrained to a plane and the colloid thus resembles a two-dimensional fluid. But the exchange of particle momentum takes place in three-dimensional space through hydrodynamic interactions in the ambient fluid.

Here we study the colloidal diffusivity starting from the Smoluchowski equation. We show that the diffusivity exhibits an intermediate behavior between purely two-dimensional and fully three-dimensional fluid: on the one hand, Fick’s law, which pertains to collective diffusion, breaks down altogether, as confirmed experimentally. On the other hand, the coefficient of self-diffusion is finite, but the transitional nature of the monolayer shows up in a non-analytic dependence on the colloidal packing fraction, at odds with the case of a fully three-dimensional colloid.