Near-field heat transfer between a nanoparticle and a rough surface

TL;DR

This paper investigates how surface roughness affects near-field heat transfer between a nanoparticle and a rough surface, revealing regimes where roughness enhances or diminishes heat flux.

Contribution

It introduces a second-order perturbation theory to analytically and numerically analyze the impact of surface roughness on near-field radiative heat transfer.

Findings

Heat transfer exceeds flat surface levels at short distances.

Surface polariton scattering reduces heat transfer at larger distances.

Results converge to proximity approximation at very small distances.

Abstract

In this work we focus on the surface roughness correction to the near-field radiative heat transfer between a nanoparticle and a material with a rough surface utilizing a direct perturbation theory up to second order in the surface profile. We discuss the different distance regimes for the local density of states above the rough material and the heat flux analytically and numerically. We show that the heat transfer rate is larger than that corresponding to a flat surface at short distances. At larger distances it can become smaller due to surface polariton scattering by the rough surface. For distances much smaller than the correlation length of the surface profile, we show that the results converge to a proximity approximation, whereas in the opposite limit the rough surface can be replaced by an equivalent surface layer.