Strong slowing down of the thermalization process of solids interacting in extreme near-field regime

TL;DR

This paper investigates the significant slowdown in the thermalization process of solids at nanometric distances in the extreme near-field regime, where heat exchange mechanisms dominate over internal conduction, affecting thermal dynamics.

Contribution

It reveals a strong slowing down of thermal relaxation in the extreme near-field regime, highlighting an increased effective thermal inertia at nanometric scales.

Findings

Thermalization slows down significantly at nanometric gaps.

Heat flux can dominate over internal conduction in this regime.

Thermal state evolution is strongly affected by near-field effects.

Abstract

When two solids at different temperatures are separated by a vacuum gap they relax toward their equilibrium state by exchanging heat either by radiation, phonon or electron tunneling, depending on their separation distance and on the nature of materials. The interplay between this exchange of energy and its spreading through each solid entirely drives the relaxation dynamics. Here we highlight a significant slowing down of this process in the extreme near-field regime at distances where the heat flux exchanged between the two solids is comparable or even dominates over the flux carried by conduction inside each solid. This mechanism, leading to a strong effective increase of the system thermal inertia, should play an important role in the temporal evolution of thermal state of interacting solids systems at nanometric and subnanometric scales.