Equilibrium long-ranged charge correlations at the interface between media coupled to the electromagnetic radiation

TL;DR

This paper investigates quantum surface charge correlations at media interfaces, revealing that in the retarded regime, the quantum prefactor simplifies to its static classical form regardless of temperature.

Contribution

It derives explicit formulas for long-range charge correlation decay prefactors considering both retarded and non-retarded regimes using fluctuational electrodynamics.

Findings

Retarded regime prefactor matches static classical form at all temperatures.

Explicit decay prefactors are obtained for various media configurations.

Analysis covers both non-retarded and retarded electromagnetic interactions.

Abstract

We continue studying long-ranged quantum correlations of surface charge densities on the interface between two media of distinct dielectric functions which are in thermal equilibrium with the radiated electromagnetic field. Two regimes are considered: the non-retarded one with the speed of light $c$ taken to be infinitely large and the retarded one with finite value of $c$. The analysis is based on results obtained by using fluctuational electrodynamics in [L. \v{S}amaj and B. Jancovici, Phys. Rev. E {\bf 78}, 051119 (2008)]. Using an integration method in the complex plane and the general analytic properties of dielectric functions in the frequency upper half-plane, we derive explicit forms of prefactors to the long-range decay of the surface charge correlation functions for all possible media (conductor, dielectric, vacuum) configurations. The main result is that the time-dependent quantum prefactor in the retarded regime takes its static classical form, for any temperature.