Near-field focusing and amplification of tip-substrate radiative heat transfer

TL;DR

This paper investigates how a thin polar film on a substrate can enhance and focus near-field radiative heat transfer between a nanoscale probe and the substrate, enabling active control at the nanoscale.

Contribution

It demonstrates that a thin polar film can actively enhance and focus near-field heat transfer, revealing a new method for controlling nanoscale thermal radiation.

Findings

Introduction of a polar film enhances heat transfer.

Film induces lateral focusing of heat exchange.

Control depends on film thickness and substrate permittivity.

Abstract

The spatially resolved near-field radiative heat transfer between a nanoscale probe and a substrate is studied in the fluctuational electrodynamics framework within the dipolar approximation. It is shown that the introduction of a thin polar film atop a non-dispersive substrate can lead to both an enhancement and a lateral focusing of the heat exchange. The influence of the probe--substrate separation, film thickness and substrate permittivity is analyzed, revealing that the effect originates from near-field interactions governed by the interplay between film-induced modifications of electromagnetic mode dispersion and the distance-dependent coupling strength. The results highlight a viable route toward the active control of local radiative heat transfer at the nanoscale.