Van der Waals interactions between atoms and dispersive
surfaces at finite temperature |
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Authors: | M-P Gorza M Ducloy |
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Institution: | (1) Laboratoire de Physique des Lasers, UMR 7538 du CNRS, Institut Galilée, Université Paris-Nord, 99 avenue J.-B. Clément, 93430 Villetaneuse, France |
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Abstract: | 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. |
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Keywords: | |
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