Metamaterial-enhanced near-field radiative heat transfer

When radiative thermal energy is exchanged at near field, evanescent surface waves such as surface phonon polaritons can tunnel through the gap, boosting heat transfer above the far-field blackbody limit by several orders of magnitude^1,2. Such extreme radiative energy fluxes have been experimentally demonstrated in dielectric materials supporting surface phonon polaritons^3-5. Although theories and simulations have suggested metamaterials as a promising route to further manipulate and enhance near-field radiative heat exchange beyond the limits of unstructured Drude- or Lorentz-type materials^6-10, experimental validation remains elusive. Here we experimentally demonstrate metamaterial-mediated enhancement on near-field radiative heat transfer between gold split-ring resonators patterned on silicon nitride (SiN) membranes. Compared with unstructured gold plates on the SiN membrane or bare SiN membranes, the radiative heat transfer between the metamaterials is enhanced several-fold. This observed enhancement results from the split-ring-resonator resonant modes and their strong coupling with surface phonon polaritons in the SiN membrane, as supported by direct electromagnetic simulations and coupled-mode-theory modelling. Our work provides experimental verification of the strong capability of metamaterials in manipulating radiative energy exchange at near field, opening opportunities for thermal energy harvesting and infrared sensing applications.