Effects of spatial dispersion in near-field radiative heat transfer between two parallel metallic surfaces

We study the heat transfer between two parallel metallic semi-infinite media with a gap in the nanometer-scale range. We show that the near-field radiative heat flux saturates at distances smaller than the metal skin depth when using a local dielectric constant and investigate the origin of this effect. The effect of non-local corrections is analysed using the Lindhard-Mermin and Boltzmann-Mermin models. We find that local and non-local models yield the same heat fluxes for gaps larger than 2 nm. Finally, we explain the saturation observed in a recent experiment as a manifestation of the skin depth and show that heat is mainly dissipated by eddy currents in metallic bodies.Comment: Version without figures (8 figures in the complete version

Nanoscale thermal radiation between two gold surfaces

In this letter, we measured the nanoscale thermal radiation between a microsphere and a substrate which were both coated with thick gold films. Although gold is highly reflective for thermal radiation, the radiative heat transfer between two gold surfaces was demonstrated to be significantly enhanced at nanoscale gaps beyond the blackbody radiation limit due to the tunneling of non-resonant evanescent waves. The measured heat transfer coefficient between two gold surfaces agreed well with theoretical prediction. At a gap d = 30 nm ± 5 nm, the heat transfer coefficient between two gold surfaces was observed to be as large as ∼400 W/m[superscript 2]·K, much greater than the blackbody radiation limit (∼5 W/m[superscript 2]·K).United States. Dept. of Energy. Office of Basic Energy Sciences (DE-FG02-02ER45977)United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiativ