Three-body Casimir effects and nonmonotonic forces

Abstract

Casimir interactions are not pairwise additive. This property leads to collective effects that we study for a pair of objects near a conducting wall. We employ a scattering approach to compute the interaction in terms of fluctuating multipoles. The wall can lead to a nonmonotonic force between the objects. For two atoms with anisotropic electric and magnetic dipole polarizabilities, we demonstrate that this nonmonotonic effect results from a competition between two- and three-body interactions. By including higher-order multipoles we obtain the force between two macroscopic metallic spheres for a wide range of sphere separations and distances to the wall.