Interatomic van der Waals potential in the presence of a magneto-electric sphere

TL;DR

This paper derives and analyzes the van der Waals potential between two atoms near a magnetoelectric sphere, revealing how the sphere's size and properties influence atomic interactions through electromagnetic effects.

Contribution

It provides a general formula for the van der Waals potential in the presence of a magnetoelectric sphere and explores its behavior across different sphere sizes, including asymptotic limits.

Findings

Potential approaches that of two atoms near a planar interface for large spheres.

For very small spheres, the potential reduces to a three-atom nonadditive interaction.

Numerical results show enhancement or reduction of interactions depending on sphere properties.

Abstract

On the basis of a general formula obtained earlier via fourth-order erturbation theory within the framework of macroscopic quantum electrodynamics, the van der Waals potential between two neutral, unpolarized, ground-state atoms in the presence of a homogeneous, dispersing and absorbing magnetoelectric sphere is studied. When the radius of the sphere becomes sufficiently large, the result asymptotically agrees with that for two atoms near a planar interface. In the opposite limit of a very small sphere, the sphere can effectively be regarded as being a third ground-state atom, and the nonadditive three-atom van der Waals potential is recovered. To illustrate the effect of a sphere of arbitrary radius, numerical results are presented for the triangular arrangement where the atoms are at equidistance from the sphere, and for the linear arrangement where the atoms and the sphere are aligned along a straight line. As demonstrated, the enhancement or reduction of the interaction potential in the presence of purely electric or magnetic spheres can be physically understood in terms of image charges.