Control of the near-field radiative heat transfer between graphene-coated nanoparticle metasurfaces

The control of near-field radiative heat transfer (NFRHT) between two metasurfaces can be achieved by manipulating the geometric and dielectric parameters of their components. Based on a 2D effective medium approximation, we describe the dielectric response of each metasurface composed of graphene-coated nanoparticles (GCNPs) on a 2D square lattice as a homogeneous uniaxial film. Wrapping Drude-like nanoparticles (NPs) with graphene enhances the effective plasmonic response of metasurfaces by significantly broadening the frequency range in which surface and hyperbolic waves can be excited by thermal photons. Consequently, the NFRHT between GCNP metasurfaces improves that observed between uncoated Drude-like nanoparticle arrays. We found that the heat flux (Q) grows with increasing metasurface packing fraction (PF) and is also sensitive to GCNP size. By tuning the graphene chemical potential \((\mu )\) $(\mu )$ , Q reaches a maximum improvement of \(88\%\) $88\%$ for \(\mu \approx 0.1\) $\mu \approx 0.1$ eV with cores made of Drude-like material, while using cores made of the polar dielectric SiC, Q increases up to \(226\%\) $226\%$ for \(\mu \approx 0.45\) $\mu \approx 0.45$ eV. Our results show that, in addition to the geometric control achieved with uncoated NP arrays, the tunable optical properties of the graphene shell allow dynamic control of the heat flux, expanding the possibilities for NFRHT engineering offered by GCNP metasurfaces.