Three-body critical Casimir forces

TL;DR

This study uses mean-field theory to analyze universal scaling functions of critical Casimir forces among three parallel cylindrical colloids in a near-critical binary mixture, revealing complex force behaviors including sign changes influenced by temperature and geometry.

Contribution

It provides the first detailed calculation of three-body critical Casimir forces for cylindrical colloids, highlighting their dependence on geometry, temperature, and boundary conditions.

Findings

Three-body forces can change sign depending on temperature and configuration.

Three-body contributions are more significant at small surface-to-surface distances.

Results are comparable to three-atom van der Waals interactions.

Abstract

Within mean-field theory we calculate universal scaling functions associated with critical Casimir forces for a system consisting of three parallel cylindrical colloids immersed in a near-critical binary liquid mixture. For several geometrical arrangements and boundary conditions at the surfaces of the colloids we study the force between two colloidal particles along their center-to-center axis, analyzing the influence of the presence of a third particle on that force. Upon changing temperature or the relative positions of the particles we observe interesting features such as a change of sign of this force caused by the presence of the third particle. We determine the three-body component of the forces acting on one of the colloids by subtracting the pairwise forces from the total force. The three-body contribution to the total critical Casimir force turns out to be more pronounced for small surface-to-surface distances between the colloids as well as for temperatures close to criticality. Moreover we compare our results with similar ones for other physical systems such as three atoms interacting via van der Waals forces.