An excited atom interacting with a Chern insulator: towards a far-field resonant Casimir-Polder repulsion

TL;DR

This paper explores how a Chern insulator's Hall conductance influences the resonant Casimir-Polder interaction with an excited atom, revealing conditions for enhanced and repulsive forces at specific frequencies and polarizations.

Contribution

It introduces the effect of Hall conductance on resonant Casimir-Polder interactions and identifies conditions for repulsive forces based on atomic polarization and Chern number.

Findings

Resonant Casimir-Polder shift is enhanced near van Hove singularities.

Repulsive Casimir-Polder force occurs at large distances for specific polarizations and Chern numbers.

The Hall conductance modifies the interaction depending on atomic polarization.

Abstract

We consider the resonant Casimir-Polder interaction of an excited alkali-type atom which has a single (electric dipole) transition with a Chern insulator. The Chern insulator has a nonzero, time reversal symmetry breaking Hall conductance, leading to an additional contribution to the resonant Casimir-Polder interaction which depends on the coupling between the Hall conductance and the circular polarization state of the atomic transition. We find that the resonant Casimir-Polder shift can be significantly enhanced for de-excitation frequencies near values associated with the van Hove singularities of the Chern insulator. Furthermore, we find that the resonant Casimir-Polder force can become monotonically decaying and repulsive for a relatively large atom-surface distance, if the atomic dipole transition is right circularly polarized and the Chern number of the Chern insulator is $-1$ or the atomic dipole transition is left circularly polarized and the Chern number is $1$.