Non-monotonic radiative heat transfer in the transition from far field to near field

TL;DR

This study measures radiative heat transfer between a glass microsphere and various substrates, revealing non-monotonic behavior during the transition from far-field to near-field due to complex three-body interactions.

Contribution

It provides high-precision experimental data on non-monotonic radiative heat transfer in a three-body system, highlighting the role of dressed emission mechanisms.

Findings

Non-monotonic flux behavior observed during near-field transition

Behavior linked to singularities in dressed emission mechanisms

Experimental validation of complex three-body radiative interactions

Abstract

We present high precision measurements of the radiative heat transfer of a glass microsphere immersed in a thermal bath in vacuum facing three different planar substrates (SiO2, SiC and Au), which exhibit very different optical behaviors in the infrared region. Using a thermoresistive probe on a cantilever, we show the nonmonotonic behavior of the radiative flux between the microsphere and its environment when the microsphere is brought closer to the substrate in the far-field to near-field transition regime. We demonstrate that this unexpected behavior is related to the singularities of dressed emission mechanisms in this three-body system sphere-substrate-bath with respect to the separation distance.