Dynamical Casimir-Polder force between an excited atom and a conducting wall

TL;DR

This paper studies the time-dependent Casimir-Polder force on an excited atom near a conducting wall, revealing oscillatory behavior and conditions under which the static force is recovered, highlighting observable dynamical effects.

Contribution

It provides a detailed analysis of the dynamical Casimir-Polder force for an excited atom, including its oscillatory nature and conditions for static force recovery, extending previous ground-state studies.

Findings

Force oscillates between attractive and repulsive over time and space.

Large dynamical forces on excited atoms make the effect easier to observe.

Static force is recovered after a certain timescale related to atomic self-dressing.

Abstract

We consider the dynamical atom-surface Casimir-Polder force in the non-equilibrium configuration of an atom near a perfectly conducting wall, initially prepared in an excited state with the field in its vacuum state. We evaluate the time-dependent Casimir-Polder force on the atom, and find that it shows an oscillatory behavior from attractive to repulsive both in time and in space. We also investigate the asymptotic behavior in time of the dynamical force and of related local field quantities, showing that the static value of the force, as obtained by a time-independent approach, is recovered for times much larger than the timescale of the atomic self-dressing, but smaller than the atomic decay time. We then discuss the evolution of global quantities such as atomic and field energies, and their asymptotic behavior. We also compare our results for the dynamical force on the excited atom with analogous results recently obtained for an initially bare ground-state atom. We show that new relevant features are obtained in the case of an initially excited atom, for example much larger values of the dynamical force with respect to the static one, allowing for an easier way to single-out and observe the dynamical Casimir-Polder effect.