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Photons typically do not contribute to thermal transport within a solid due to their low energy density and tendency to be absorbed quickly. We propose a practical material system—infrared plasmonic resonators embedded in a semiconductor nanowire—that leverages near-field electromagnetic coupling to achieve photonic thermal transport comparable to the electronic and phononic contributions. We analytically show photonic thermal conductivities up to about 1 W m−1 K−1 for 10 nm diameter Si and InAs nanowires containing repeated resonators at 500 K. The nanowire system outperforms plasmonic particles in isotropic environments and presents a pathway for photonic thermal transport to exceed that of phonons and electrons. [ABSTRACT FROM AUTHOR]

• Compared approaches to near-field radiative heat transfer in nanoparticle chains. • Calculated radiative thermal conductivity for different materials and spacings. • Showed that kinetic theory is valid for strong coupling by surface polaritons. • Fluctuational electrodynamics is needed when kinetic theory assumptions fail. In chains of closely spaced nanoparticles supporting surface polaritons, near-field electromagnetic coupling leads to collective effects and super-Planckian thermal radiation exchange. Researchers have primarily used two analytical approaches to calculate radiative heat transfer in these systems: fluctuational electrodynamics, which directly incorporates fluctuating thermal currents into Maxwell's equations, and a kinetic approach where the dispersion relation provides modes and propagation lengths for the Boltzmann transport equation. Here, we compare results from the two approaches in the isotropic dipole limit in order to identify regimes in which kinetic theory is valid and to explain differing results in the literature on its validity. Using both methods, we calculate the diffusive radiative thermal conductivity of nanoparticle chains. We show that kinetic theory is valid and matches predictions by fluctuational electrodynamics if both the surface polariton propagation lengths are greater than the particle spacing and surface polaritons are the dominant contributors to radiative heat transfer. [ABSTRACT FROM AUTHOR]