Casimir attraction in multilayered plane parallel magnetodielectric systems

A powerful procedure is presented for calculating the Casimir attraction between plane parallel multilayers made up of homogeneous regions with arbitrary magnetic and dielectric properties by use of the Minkowski energy-momentum tensor. The theory is applied to numerous geometries and shown to reproduce a number of results obtained by other authors. Although the various pieces of theory drawn upon are well known, the relative ease with which the Casimir force density in even complex planar structures may be calculated, appears not to be widely appreciated, and no single paper to the author's knowledge renders explicitly the procedure demonstrated herein. Results may be seen as an important building block in the settling of issues of fundamental interest, such as the long-standing dispute over the thermal behaviour of the Casimir force or the question of what is the correct stress tensor to apply, a discussion re-quickened by the newly suggested alternative theory due to Raabe and Welsch.Comment: 13 pages, 6 figures. Version 2: Updated contact details. Minor changes and correction

Surface Enhanced van der Waals force

We consider the van der Waals interaction of an excited atom and a ground state atom across a vacuum-medium interface under the circumstances of the resonant coupling of the excited atom to a surface polariton mode of the system. We demonstrate that the nonretarded interaction potential between the atoms is in this case the same as in an effective medium described by the average dielectric function of the media in contact except for the different local-field correction factor. The estimate performed for the vacuum-sapphire interface shows that the nonretarded van der Waals (atom*-atom) force can be at the surface mode resonance enhanced by almost three orders of magnitude in comparison with its free-space value. Owing to the local-field effect in the present configuration this enhancement factor is larger then previously estimated for atoms in front of the same medium by (almost) an order of magnitude.Comment: 6 pages, 2 figures; presented at CEWQO08, Belgrade, Serbia, 30 May-03 June 200

Medium-modified Casimir forces

We argue that the results for the vacuum forces on a slab and on an atom embedded in a magnetodielectric medium near a mirror, obtained using a recently suggested Lorentz-force approach to the Casimir effect, are equivalent to the corresponding results obtained in a traditional way. We also derive a general expression for the atom-atom force in a medium and extend a few classical results concerning this force in vacuum and dielectrics to magnetodielectric systems. This, for example, reveals that the (repulsive) interaction between atoms of different polarizability type is at small distances unaffected by a (weakly polarizable) medium.Comment: 5 pages, 1 figure, reinterpreted and revise

Vakuumska sila potpomognuta sredstvom

We discuss some implications of a very recently obtained result for the force on a slab in a planar cavity based on the calculation of the vacuum Lorentz force [C. Raabe and D.-G. Welsch, Phys. Rev. A 71 (2005) 013814]. We demonstrate that, according to this formula, the total force on the slab consists of a medium-screened Casimir force and, in addition to it, a medium-assisted force. The sign of of the medium-assisted force is determined solely by the properties of the cavity mirrors. In the Lifshitz configuration, this force is proportional to 1/d at small distances and is very small compared with the corresponding van der Waals force. At large distances, however, it is proportional to 1/d4 and comparable with the Casimir force, especially for denser media. The exponents in these power laws decrease by 1 in the case of a thin slab. The formula for the medium-assisted force also describes the force on a layer of the cavity medium, which has similar properties. For dilute media, it implies an atom-mirror interaction of the Coulomb type at small and of the Casimir-Polder type at large atom-mirror distances. For a perfectly reflecting mirror, the latter force is effectively only three-times smaller than the Casimir-Polder force.Raspavljamo implikacije nedavno dobivenog rezultata za silu na neku ploču u planarnom rezonatoru baziranom na proračunu vakuumske Lorentzove sile [C. Raabe and D.-G. Welsch, Phys. Rev. A 71 (2005) 013814]. Prema toj formuli, ukupna se sila na ploču sastoji od zasjenjene Casimirove sile i sredstvom potpomognute sile čiji je predznak određen isključivo svojstvima zidova rezonatora. U Lifshitzovoj konfiguraciji, ova sila je proporcionalna 1/d na malim udaljenostima i jako mala u usporedbi s odgovarajućom van der Waalsovom silom. Međutim, na velikim udaljenostima ona je proporcionalna 1/d4 i usporediva s Casimirovom silom, posebno za gušća sredstva u rezonatoru. U slučaju tankog sloja, ova asimptotska ponašanja prelaze u 1/d2 odnosno 1/d5 . Formula za sredstvom potpomognutu silu opisuje također silu na neki sloj sredstva u rezonatoru, koja ima slična svojstva. Za razrijeđena sredstva, ona implicira interakciju atom-zid Coulombovog tipa na malim i Casimir-Polder tipa na velikim udaljenostima. U slučaju idealno reflektirajućeg zida, ova sila je efektivno samo tri puta slabija od Casimir-Polderove sile

Vakuumska sila potpomognuta sredstvom

We discuss some implications of a very recently obtained result for the force on a slab in a planar cavity based on the calculation of the vacuum Lorentz force [C. Raabe and D.-G. Welsch, Phys. Rev. A 71 (2005) 013814]. We demonstrate that, according to this formula, the total force on the slab consists of a medium-screened Casimir force and, in addition to it, a medium-assisted force. The sign of of the medium-assisted force is determined solely by the properties of the cavity mirrors. In the Lifshitz configuration, this force is proportional to 1/d at small distances and is very small compared with the corresponding van der Waals force. At large distances, however, it is proportional to 1/d4 and comparable with the Casimir force, especially for denser media. The exponents in these power laws decrease by 1 in the case of a thin slab. The formula for the medium-assisted force also describes the force on a layer of the cavity medium, which has similar properties. For dilute media, it implies an atom-mirror interaction of the Coulomb type at small and of the Casimir-Polder type at large atom-mirror distances. For a perfectly reflecting mirror, the latter force is effectively only three-times smaller than the Casimir-Polder force.Raspavljamo implikacije nedavno dobivenog rezultata za silu na neku ploču u planarnom rezonatoru baziranom na proračunu vakuumske Lorentzove sile [C. Raabe and D.-G. Welsch, Phys. Rev. A 71 (2005) 013814]. Prema toj formuli, ukupna se sila na ploču sastoji od zasjenjene Casimirove sile i sredstvom potpomognute sile čiji je predznak određen isključivo svojstvima zidova rezonatora. U Lifshitzovoj konfiguraciji, ova sila je proporcionalna 1/d na malim udaljenostima i jako mala u usporedbi s odgovarajućom van der Waalsovom silom. Međutim, na velikim udaljenostima ona je proporcionalna 1/d4 i usporediva s Casimirovom silom, posebno za gušća sredstva u rezonatoru. U slučaju tankog sloja, ova asimptotska ponašanja prelaze u 1/d2 odnosno 1/d5 . Formula za sredstvom potpomognutu silu opisuje također silu na neki sloj sredstva u rezonatoru, koja ima slična svojstva. Za razrijeđena sredstva, ona implicira interakciju atom-zid Coulombovog tipa na malim i Casimir-Polder tipa na velikim udaljenostima. U slučaju idealno reflektirajućeg zida, ova sila je efektivno samo tri puta slabija od Casimir-Polderove sile

Recursion relations for generalized Fresnel coefficients: Casimir force in a planar cavity

We emphasize and demonstrate that, besides using the usual recursion relations involving successive layers, generalized Fresnel coefficients of a multilayer can equivalently be calculated using the recursion relations involving stacks of layers, as introduced some time ago [M. S. Tomas, Phys. Rev. A 51, 2545 (1995)]. Moreover, since the definition of the generalized Fresnel coefficients employed does not imply properties of the stacks, these nonstandard recursion relations can be used to calculate Fresnel coefficients not only for local systems but also for a general multilayer consisting of various types (local, nonlocal, inhomogeneous etc.) of layers. Their utility is illustrated by deriving a few simple algorithms for calculating the reflectivity of a Bragg mirror and extending the formula for the Casimir force in a planar cavity to arbitrary media.Comment: 5 pages, 2 figures, slightly expande

Vacuum force on an atom in a magnetodielectric cavity

We demonstrate that, according to a recently suggested Lorentz-force approach to the Casimir effect, the vacuum force on an atom embedded in a material cavity differs substantially from the force on an atom of the cavity medium. The force on an embedded atom is of the familiar (van der Waals and Casimir-Polder) type, however, more strongly modified by the cavity medium than usually considered. The force on an atom of the cavity medium is of the medium-assisted force type with rather unusual properties, as demonstrated very recently [M. S. Tomas, Phys. Rev. A 71, 060101(R) (2005)]. This implies similar properties of the vacuum force between two atoms in a medium.Comment: RevTeX 4, 4 pages, 1 eps figure, corrected and slightly revise

Enhanced van der Waals interaction at interfaces

Using a recently obtained (general) formula for the interaction energy between an excited and a ground-state atom (Sherkunov Y 2007 Phys. Rev. A 75 012705), we consider the interaction energy between two such atoms near the interface between two media. We demonstrate that under the circumstances of the resonant coupling of the excited atom to the surface polariton mode of a vacuum-medium system the nonretarded atom*-atom interaction energy can be enhanced by (several) orders of magnitude in comparison with the van der Waals interaction energy of the two isolated atoms.Comment: 8 pages, 5 figures, local-field corrections included and improved presentatio

Matter-screened Casimir force and Casimir-Polder force in planar structures

Using a recently developed theory of the Casimir force (Raabe C and Welsch D-G 2005 Phys. Rev. A 71 013814), we calculate the force that acts on a plate in front of a planar wall and the force that acts on the plate in the case where the plate is part of matter that fills the space in front of the wall. We show that in the limit of a dielectric plate whose permittivity is close to unity, the force obtained in the former case reduces to the ordinary, i.e., unscreened Casimir-Polder force acting on isolated atoms. In the latter case, the theory yields the Casimir-Polder force that is screened by the surrounding matter.Comment: 11 pages, 1 figure -- published online at J. Opt. B on Nov 16 200

Long-range surface plasmon polariton excitation at the quantum level

We provide the quantum mechanical description of the excitation of long-range surface plasmon polaritons (LRSPPs) on thin metallic strips. The excitation process consists of an attenuated-reflection setup, where efficient photon-to-LRSPP wavepacket-transfer is shown to be achievable. For calculating the coupling, we derive the first quantization of LRSPPs in the polaritonic regime. We study quantum statistics during propagation and characterize the performance of photon-to-LRSPP quantum state transfer for single-photons, photon-number states and photonic coherent superposition states.Comment: 9 pages, 6 figures, RevTeX4; Accepted versio