Nonmonotonic near-field heat transfer between a pair of spheres

Abstract

We study near-field radiative heat exchange between a pair of equal and unequal radii of spheres, exploring the effects of material properties, sphere radii, and separation distances by following the exact mathematical solution. Previous studies suggested that larger area of the object transfer larger heat compared to smaller area of the object. However, our study reveals that this is not always true. We propose the first way to achieve unique results such that the conductance can be higher for a smaller area of the spheres. For equal-sized spheres, the thermal conductance increases with radius due to enhanced resonant coupling in tellurium and surface phonon polaritons in silicon dioxide. For unequal radii, we observe non-monotonic conductance trends in tellurium caused by hybridization of resonant modes. The role of Mie resonance in SiC, which is associated with size dependent effects and non-monotonic trends in both symmetric and asymmetric configurations, is highlighted. Quasi-Normal Mode analysis highlights the role of coupled resonances in modulating heat transfer.