Mode structure and polaritonic contributions to the Casimir effect in a magneto-dielectric cavity

TL;DR

This paper analyzes the mode spectrum in a magneto-dielectric cavity, revealing how surface polaritons influence the Casimir effect and can lead to repulsive forces at small separations.

Contribution

It provides a full dispersion relation analysis for a cavity with magneto-dielectric and metallic walls, highlighting the role of surface polaritons in the Casimir effect.

Findings

Surface polaritons dominate the Casimir interaction at small separations.

s-polarized polaritons are key in the potential for repulsive Casimir forces.

Closed-form dispersion relations are derived for realistic material models.

Abstract

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.