Limitations of the kinetic theory to describe the near-field heat exchanges in many-body systems

TL;DR

This paper compares kinetic and exact electrodynamics methods for heat transfer in nanoparticle chains, revealing significant limitations of the kinetic approach especially in near-field and ballistic regimes.

Contribution

It demonstrates the failure of kinetic theory to accurately predict near-field heat transfer in many-body nanoparticle systems compared to Landauer's approach.

Findings

Kinetic theory underestimates heat flux in near-field regimes.

Deviation between methods reaches a factor of two in diffusive regimes.

Differences exceed two orders of magnitude in ballistic regimes.

Abstract

We investigate the radiative heat transfer along a chain of nanoparticles using both a purely kinetic approach based on the solution of a Boltzmann transport equation and an exact method (Landauer's approach) based on fluctuational electrodynamics. We show that the kinetic theory generally fails to predict properly the heat flux transported along the chain both at close (near-field regime) and large separation (far-field regime) distances. We report a deviation of a factor two between the heat fluxes predicted by the two approaches in the diffusive regime of heat transport and we show that this difference becomes even greater than two orders of magnitude in the ballistic regime.