Repulsive Casimir-Lifshitz pressure in closed cavities

TL;DR

This paper extends the understanding of Casimir-Lifshitz forces to spherical geometries, showing conditions under which the pressure can be repulsive, which could impact nanotechnology and material science.

Contribution

It generalizes the sign determination of Casimir-Lifshitz pressure to spherical cavities using a scattering formalism, beyond previous slab-based results.

Findings

The pressure can be repulsive in certain configurations.

The sign of the force is independent of cavity geometry at thermal equilibrium.

Configurations are identified where the sphere experiences expansion due to Casimir-Lifshitz forces.

Abstract

We consider the interaction pressure acting on the surface of a dielectric sphere enclosed within a magnetodielectric cavity. We determine the sign of this quantity regardless of the geometry of the cavity for systems at thermal equilibrium, extending the Dzyaloshinskii-Lifshitz-Pitaevskii result for homogeneous slabs. As in previous theorems regarding Casimir-Lifshitz forces, the result is based on the scattering formalism. In this case the proof follows from the variable phase approach of electromagnetic scattering. With this, we present configurations in which both the interaction and the self-energy contribution to the pressure tend to expand the sphere.