Dresden 2009 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 1: Statistical physics I (general)
DY 1.2: Vortrag
Montag, 23. März 2009, 10:45–11:00, HÜL 386
Critical Casimir force for films in the crossover between various surface universality classes — •Thomas Friedrich Mohry1,2, Anna Maciołek1,2, and Siegfried Dietrich1,2 — 1Max-Planck-Institut für Metallforschung, Heisenbergstraße 3, 70569 Stuttgart, Germany — 2Universität Stuttgart, Institut für Theoretische und Angewandte Physik, Pfaffenwaldring 57, 70569 Stuttgart, Germany
The critical Casimir force and the order-parameter profiles in thin films belonging to the Ising universality class are studied field theoretically, focusing on the crossovers between various surface universality classes. The corresponding universal scaling functions are calculated within mean-field theory. For both the crossover between the normal and the special transition and for the crossover between the normal and the ordinary transition, the scaling function of the critical Casimir force exhibits a rich structure, such as the emergence of several extrema. Depending on the choice of the surface properties, as described by surface fields or surface enhancement parameters, the critical Casimir force can change its sign once or twice by varying the temperature. A simple relation between the sign of the force and the values of the order-parameter at the surfaces and in the bulk is presented. The results are relevant for colloidal systems in the presence of a critical solvent and for wetting films near critical end points.