Dynamics of Near-Field Radiative Heat Transfer in Ensembles of Nanostructures

The thermal radiation exchanged between bodies separated by macroscopic distances is accurately described by Planck's law. However, this description breaks down when the distance between objects or their size becomes significantly smaller than the so-called thermal wavelength. In this limit, the contribution of near-field components of the electromagnetic field, together with the strong responses provided by the optical resonances of nanostructures, results in enhanced radiative heat transfer, which can surpass the blackbody limit by several orders of magnitude. We introduce a theoretical framework to describe the temporal dynamics of near-field heat radiative heat exchange in ensembles of nanostructures, which is based on the use of an eigenmode expansion of the equations that govern this process. Using this formalism, we identify the fundamental principles that determine the thermalization of collections of nanostructures, revealing general but often unintuitive dynamics. Our results provide an elegant, precise, and efficient approach to investigate the temporal dynamics of radiative heat transfer in systems containing a large number of nanoparticles.