Nanomaterials - 20

Abstract

Superlattices are well-known for their low interfacial thermal conductance, posing a persistent challenge in facilitating heat flow across the interface. Contrary to heat conduction, radiation offers an alternative pathway for efficient thermal transport and attributes to overall heat transfer rate. Inspired by the recent discovery of surprising large radiative heat flux in hyperbolic metamaterials of hBN, we explored the superlattice nanostructures composed of alternatively cascaded polar dielectric thin films using the fluctuational electrodynamics. It shows that, in these nanolaminated hyperbolic metamaterials, internal radiative heat flux can research the same order of magnitude as conductive heat flux due to efficient transport of hyperbolic phonon-polaritons, the electromagnetic modes arising from the coupling of photons and phonons with large out-of-plane wavenumbers. When coupled with a metallic thin film populated by hot electrons, quasi-particles that are out of equilibrium with the lattice and carry excess energy, plasmon-polaritons can traverse the hyperbolic/metallic interface, enabling radiative heat fluxes on the order of 107 W/m2. The efficiency of this transport mechanism is highly sensitive to the electron temperature. These nanolaminated hyperbolic metamaterials challenge the conventional paradigm of solid-state heat transfer that has long been dominated by phonon and electron conduction.