Van der Waals interactions between excited atoms in generic environments

TL;DR

This paper develops a dynamical theory for van der Waals interactions involving excited atoms in complex environments, revealing distance-dependent force behaviors and population-induced dynamics.

Contribution

It introduces a dynamical approach to describe van der Waals forces between excited atoms in magnetodielectric environments, connecting force oscillations to atomic states.

Findings

Large-distance forces are monotonic for ground-state atoms.

Excited atoms experience spatially oscillating van der Waals forces.

Atoms decay to ground states, leading to standard van der Waals interactions.

Abstract

We consider the the van der Waals force involving excited atoms in general environments, constituted by magnetodielectric bodies. We develop a dynamical approach studying the dynamics of the atoms and the field, mutually coupled. When only one atom is excited, our dynamical theory suggests that for large distances the van der Waals force acting on the ground-state atom is monotonic, while the force acting in the excited atom is spatially oscillating. We show how this latter force can be related to the known oscillating Casimir--Polder force on an excited atom near a (ground-state) body. Our force also reveals a population-induced dynamics: for times much larger that the atomic lifetime the atoms will decay to their ground-states leading to the van der Waals interaction between ground-state atoms.