Casimir-Polder interaction between an atom and a small magnetodielectric sphere

TL;DR

This paper derives a comprehensive formula for the Casimir-Polder force between an atom and a small magnetodielectric sphere, accounting for complex environments and local-field effects, bridging microscopic and macroscopic interactions.

Contribution

It introduces a closed-form expression for the atom-sphere Casimir-Polder force in arbitrary environments, including local-field corrections, and compares it with van der Waals interactions.

Findings

Derived a general formula for atom-sphere Casimir-Polder force

Compared Casimir-Polder and van der Waals forces

Numerical examples illustrate the theoretical predictions

Abstract

On the basis of macroscopic quantum electrodynamics and point-scattering techniques, we derive a closed expression for the Casimir-Polder force between a ground-state atom and a small magnetodielectric sphere in an arbitrary environment. In order to allow for the presence of both bodies and media, local-field corrections are taken into account. Our results are compared with the known van der Waals force between two ground-state atoms. To continuously interpolate between the two extreme cases of a single atom and a macroscopic sphere, we also derive the force between an atom and a sphere of variable radius that is embedded in an Onsager local-field cavity. Numerical examples illustrate the theory.