Van der Waals interactions between atoms and dispersive surfaces at finite temperature
Laboratoire de Physique des Lasers, UMR 7538 du CNRS, Institut Galilée, Université Paris-Nord, 99 avenue J.-B. Clément, 93430 Villetaneuse, France
Corresponding author: a email@example.com
Revised: 12 September 2006
Published online: 1 November 2006
The long-range interactions between an atomic system in an arbitrary energy level and dispersive surfaces in thermal equilibrium at non-zero temperature are revisited within the framework of the quantum-mechanical linear response theory, using generalized susceptibilities for both atom and electromagnetic field. After defining the observables of interest, one presents a general analysis of the atomic level shift valid for any number and form of dielectric surfaces. It is shown that, at zero temperature, one recovers well-known results previously obtained in the linear response regime. The case of a plane dispersive surface is elaborated on in the non-retarded regime. Calculations are given in detail for a dielectric surface exhibiting a single polariton resonance. Theoretical predictions are presented within a physical viewpoint allowing one to discriminate between the various interaction processes: on one hand, the level shift induced by non-resonant quantum fluctuations, on the other hand, two potentially resonant atom-surface couplings. The first resonant process appears for excited-state atoms and originates in an atomic de-excitation channel resonantly coupled to the surface polariton mode. It exists also at zero temperature, and has been studied and observed previously. The second physical process, which exists at non-zero temperature only, corresponds to the reverse process in which a thermal quantum excitation of a surface polariton resonantly couples to an atomic absorption channel. This novel phenomenon is predicted as well for a ground state atom, and can turn the ordinary long-range van der Waals attraction of atoms into a surface repulsion at increasing temperatures. This opens the way to the control and engineering of the sign and amplitude of van der Waals forces via surface temperature adjustment.
PACS: 42.50.Ct – Quantum description of interaction of light and matter; related experiments / 34.50.Dy – Interactions of atoms and molecules with surfaces; photon and electron emission; neutralization of ions / 12.20.-m – Quantum electrodynamics / 42.25.Gy – Edge and boundary effects; reflection and refraction
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2006