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 nonlocal corrections is analyzed using the Lindhard-Mermin and Boltzmann-Mermin models. We find that local and nonlocal models yield the same heat fluxes for gaps larger than $2\mathrm{nm}$. 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.

• Received 3 October 2007

DOI:https://doi.org/10.1103/PhysRevB.77.035431