Near field versus far field in radiative heat transfer between two-dimensional metals

TL;DR

This paper analytically investigates radiative heat transfer between two-dimensional metallic layers, highlighting the roles of conductivity and wave contributions in different regimes, with implications for nanoscale thermal management.

Contribution

It provides a detailed analytical analysis of heat transfer mechanisms between 2D metals, emphasizing the impact of conductivity and distinguishing between near-field and far-field effects.

Findings

Evanescent waves can dominate heat transfer even at large separations for poorly conducting metals.

Magnetostatic coupling is the main contributor for well-conducting metals at small separations.

The role of dc conductivity is crucial in determining the dominant heat transfer mechanism.

Abstract

Using the standard fluctuational electrodynamics framework, we analytically calculate the radiative heat current between two thin metallic layers, separated by a vacuum gap. We analyse different contributions to the heat current (travelling or evanescent waves, transverse electric or magnetic polarization) and reveal the crucial qualitative role played by the dc conductivity of the metals as compared to the speed of light. For poorly conducting metals, the heat current may be dominated by evanescent waves even when the separation between the layers greatly exceeds the thermal photon wavelength, and the coupling is of electrostatic nature. For well-conducting metals, the evanescent contribution dominates at separations smaller than the thermal wavelength and is mainly due to magnetostatic coupling, in agreement with earlier works on bulk metals.