Fluctuations of radiative heat exchange between two bodies

TL;DR

This paper develops a theory describing fluctuations in radiative heat transfer between two bodies, highlighting significant differences between far-field and near-field regimes, especially due to surface polaritons.

Contribution

The paper introduces a theoretical framework for analyzing nonequilibrium radiative heat flux fluctuations, emphasizing the impact of surface polaritons in near-field conditions.

Findings

Variance of heat flux equals mean in far field

Variance exceeds mean by over an order in near field due to surface polaritons

Correlation time of heat flux matches carrier relaxation time

Abstract

We present a theory to describe the fluctuations of nonequilibrium radiative heat transfer between two bodies both in far and near-field regime. As predicted by the blackbody theory, in far field, we show that the variance of radiative heat flux is of the same order of magnitude as its mean value. However, in near-field regime we demonstrate that the presence of surface polaritons makes this variance more than one order of magnitude larger than the mean flux. We further show that the correlation time of heat flux in this regime is comparable to the relaxation time of heat carriers in each medium. This theory could open the way to an experimental investigation of heat exchanges far from the thermal equilibrium condition.