SKM 2023 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 54: Complex Fluids and Colloids, Micelles and Vesicles (joint session CPP/DY)

DY 54.3: Vortrag

Freitag, 31. März 2023, 10:15–10:30, MER 02

Universal Casimir interaction and its relevance for colloidal and biophysical systems — •Tanja Schoger¹, Benjamin Spreng², Gert-Ludwig Ingold¹, Paulo A. Maia Neto³, and Serge Reynaud⁴ — ¹Universität Augsburg, Germany — ²University of California at Davis, USA — ³Universidade Federal do Rio de Janeiro, Brazil — ⁴Laboratoire Kastler Brossel, France

Colloidal systems and biophysical interfaces involve electrolytic environments where the Debye screening is extremely efficient. Therefore, it was thought that the interaction induced by electromagnetic fluctuations could not give rise to long-range forces in such systems. It has now been shown and experimentally verified [1] that the contribution to the Casimir force or retarded van der Waals force induced by low-frequency transverse magnetic fluctuations is not screened. There thus exists a contribution to the long-range interaction between two objects in an electrolyte two orders of magnitude larger than previously thought at distances as small as one hundred nanometres.

For two dielectric microspheres in salted water at room temperature, the force becomes universal for sufficiently large distances, in that it depends solely on the geometrical parameters and not on dielectric functions. While in general, a significant numerical effort is required to determine the Casimir interaction [2], we have also derived approximate simple expressions [3] accurate enough for most practical applications. - [1] L. B. Pires et al., Phys. Rev. Res. 3 033037, (2021); [2] B. Spreng et al. J. Chem. Phys. 153, 024115 (2020); [3] T. Schoger et al., Phys. Rev. Lett. 128, 230602 (2022)