Tight bounds and the role of optical loss in polariton-mediated near-field heat transfer

TL;DR

This paper develops an analytical model for near-field heat transfer in plasmonic and polar materials, revealing how optical loss influences thermal conductance and establishing bounds for optimizing heat transfer performance.

Contribution

It introduces a universal analytical framework that isolates optical loss effects and provides tight bounds for near-field heat transfer in polaritonic materials.

Findings

Derived a closed-form expression for thermal conductance considering optical loss.

Identified optimal conditions for maximizing near-field heat transfer.

Established universal bounds for heat transfer performance of polaritonic materials.

Abstract

We introduce an analytical framework for near-field radiative heat transfer in bulk plasmonic and polar media. Considering material dispersion, we derive a closed-form expression for the radiative thermal conductance, which disentangles the role of optical loss from other material dispersion characteristics, such as the spectral width of the Reststrahlen band in polar dielectrics, as well as from the temperature. We provide a universal condition for maximizing heat transfer that defines the optimal interplay between a material's optical loss and polariton resonance frequency, based on which we introduce tight bounds to near-field heat transfer. With this formalism, one can quantitatively evaluate all polaritonic materials in terms of their performance as near-field thermal emitters.