Casimir-Polder potential on an excited atom near an atomic array

TL;DR

This paper presents a microscopic theory of Casimir-Polder forces on an excited atom near an atomic array, revealing how these forces depend on system parameters and bridging single-atom and macroscopic regimes.

Contribution

It introduces a detailed microscopic model for CP potentials involving atomic arrays, deriving new scaling laws and demonstrating tunability through array parameters.

Findings

Derived resonant and off-resonant CP potentials using perturbation theory.

Identified asymptotic scaling laws for CP shifts with atom-array separation.

Showed tunability of CP forces via array spacing, size, and dipole orientation.

Abstract

We develop a microscopic description of the fluctuation-mediated Casimir-Polder (CP) shifts on a 'test' two-level atom placed near a two-dimensional atomic array of two-level atoms. We derive the resonant and off-resonant CP potentials experienced by the excited test atom using fourth-order perturbation theory, under the assumption that the test atom resonance is far detuned from those of the array atoms. The total potential on the test atom can be described as the sum of the pairwise resonant and off-resonant potentials resulting from its interaction with the individual atoms of the array. We analyze the asymptotic scaling of CP shifts as a function of the test atom-array separation, and its dependence on various system parameters: array spacing and size, and dipole orientation of the array atoms. Our results bridge the description of CP potential across two distinct regimes: (i) from a single-atom limit where we recover the well-known two-atom Van der Waals potential, (ii) to a macroscopic boundary limit, where we demonstrate new asymptotic scaling laws. We demonstrate that these scaling laws can be tuned via the microscopic parameters of the atomic array, establishing atomically-controlled arrays as a versatile platform for tailoring fluctuation-induced QED phenomena.