Repulsive Casimir and Casimir-Polder Forces

TL;DR

This paper reviews the phenomenon of Casimir and Casimir-Polder repulsion, emphasizing recent analytical developments and specific geometries where repulsion can be achieved, with potential practical applications.

Contribution

It provides a comprehensive survey of recent advances in understanding Casimir repulsion, especially analytic results for anisotropic atoms and complex geometries like wedges and cylinders.

Findings

Repulsion occurs in wedge-shaped and cylindrical conductors with sufficient asymmetry.

Analytic results for anisotropically polarizable atoms and their interactions are highlighted.

Recent developments confirm and extend the understanding of Casimir repulsion phenomena.

Abstract

Casimir and Casimir-Polder repulsion have been known for more than 50 years. The general "Lifshitz" configuration of parallel semi-infinite dielectric slabs permits repulsion if they are separated by a dielectric fluid that has a value of permittivity that is intermediate between those of the dielectric slabs. This was indirectly confirmed in the 1970s, and more directly by Capasso's group recently. It has also been known for many years that electrically and magnetically polarizable bodies can experience a repulsive quantum vacuum force. More amenable to practical application are situations where repulsion could be achieved between ordinary conducting and dielectric bodies in vacuum. The status of the field of Casimir repulsion with emphasis on recent developments will be surveyed. Here, stress will be placed on analytic developments, especially of Casimir-Polder (CP) interactions between anisotropically polarizable atoms, and CP interactions between anisotropic atoms and bodies that also exhibit anisotropy, either because of anisotropic constituents, or because of geometry. Repulsion occurs for wedge-shaped and cylindrical conductors, provided the geometry is sufficiently asymmetric, that is, either the wedge is sufficiently sharp or the atom is sufficiently far from the cylinder.