655 research outputs found
The role of Surface Plasmon modes in the Casimir Effect
In this paper we study the role of surface plasmon modes in the Casimir
effect. First we write the Casimir energy as a sum over the modes of a real
cavity. We may identify two sorts of modes, two evanescent surface plasmon
modes and propagative modes. As one of the surface plasmon modes becomes
propagative for some choice of parameters we adopt an adiabatic mode definition
where we follow this mode into the propagative sector and count it together
with the surface plasmon contribution, calling this contribution "plasmonic".
The remaining modes are propagative cavity modes, which we call "photonic". The
Casimir energy contains two main contributions, one coming from the plasmonic,
the other from the photonic modes. Surprisingly we find that the plasmonic
contribution to the Casimir energy becomes repulsive for intermediate and large
mirror separations. Alternatively, we discuss the common surface plasmon
defintion, which includes only evanescent waves, where this effect is not
found. We show that, in contrast to an intuitive expectation, for both
definitions the Casimir energy is the sum of two very large contributions which
nearly cancel each other. The contribution of surface plasmons to the Casimir
energy plays a fundamental role not only at short but also at large distances.Comment: 10 pages, 3 figures. TQMFA200
Dynamical Casimir-Polder interaction between an atom and surface plasmons
We investigate the time-dependent Casimir-Polder potential of a polarizable
two-level atom placed near a surface of arbitrary material, after a sudden
change in the parameters of the system. Different initial conditions are taken
into account. For an initially bare ground-state atom, the time-dependent
Casimir-Polder energy reveals how the atom is "being dressed" by virtual,
matter-assisted photons. We also study the transient behavior of the
Casimir-Polder interaction between the atom and the surface starting from a
partially dressed state, after an externally induced change in the atomic level
structure or transition dipoles. The Heisenberg equations are solved through an
iterative technique for both atomic and field operators in the medium-assisted
electromagnetic field quantization scheme. We analyze in particular how the
time evolution of the interaction energy depends on the optical properties of
the surface, in particular on the dispersion relationof surface plasmon
polaritons. The physical significance and the limits of validity of the
obtained results are discussed in detail.Comment: 12 pages, 8 figure
Mode structure and polaritonic contributions to the Casimir effect in a magneto-dielectric cavity
We present a full analysis of the mode spectrum in a cavity formed by two
parallel plates, one of which is a magneto-dielectric, e.g. a metamaterial,
while the other one is metallic, and obtain dispersion relations in closed
form. The optical properties of the cavity walls are described in terms of
realistic models for the effective permittivity and the permeability. Surface
polaritons, i.e. electromagnetic modes that have at least partly an evanescent
character, are shown to dominate the Casimir interaction at small separations.
We analyze in detail the s-polarized polaritons, which are a characteristic
feature of a magneto-dielectric configuration, and discuss their role in the
repulsive Casimir force.Comment: 14 pages, 8 figure
Repulsive Casimir forces and the role of surface modes
The Casimir repulsion between a metal and a dielectric suspended in a liquid
has been thoroughly studied in recent experiments. In the present paper we
consider surface modes in three layered systems modeled by dielectric functions
guaranteeing repulsion. It is shown that surface modes play a decisive role in
this phenomenon at short separations. For a toy plasma model we find the
contribution of the surface modes at all distances.Comment: 13 pages, 3 figures, submitted to PR
The Casimir effect for thin plasma sheets and the role of the surface plasmons
We consider the Casimir force betweeen two dielectric bodies described by the
plasma model and between two infinitely thin plasma sheets. In both cases in
addition to the photon modes surface plasmons are present in the spectrum of
the electromagnetic field. We investigate the contribution of both types of
modes to the Casimir force and confirm resp. find in both models large
compensations between the plasmon modes themselves and between them and the
photon modes especially at large distances. Our conclusion is that the
separation of the vacuum energy into plasmon and photon contributions must be
handled with care except for the case of small separations.Comment: submitted to JPhysA Special Issue QFEXT'05, replaced due to a wrong
Latex comman
Surface plasmon modes and the Casimir energy
We show the influence of surface plasmons on the Casimir effect between two
plane parallel metallic mirrors at arbitrary distances. Using the plasma model
to describe the optical response of the metal, we express the Casimir energy as
a sum of contributions associated with evanescent surface plasmon modes and
propagative cavity modes. In contrast to naive expectations, the plasmonic
modes contribution is essential at all distances in order to ensure the correct
result for the Casimir energy. One of the two plasmonic modes gives rise to a
repulsive contribution, balancing out the attractive contributions from
propagating cavity modes, while both contributions taken separately are much
larger than the actual value of the Casimir energy. This also suggests
possibilities to tailor the sign of the Casimir force via surface plasmons.Comment: 4 pages, 3 figures, revtex
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