Enhanced Near-Field Radiative Heat Transport between Graphene Metasurfaces with Symmetric Nanopatterns

Metasurfaces, the two-dimensional analog of metamaterials, have exhibited unprecedented optical and thermal properties, including super-Planckian thermal radiation. Asymmetrically patterning two-dimensional materials has been proposed recently to excite additional surface hyperbolic modes, which can enhance radiative energy transport. In the present study, we further look into the effect of symmetric patterns. The graphene metasurfaces are selected as an example to present the improving role of symmetric patterning in radiative heat flux. Fluctuational electrodynamics that incorporates scattering matrix theory with rigorous coupled-wave analysis is employed to exactly calculate the near-field heat flux. It is shown that the radiative heat flux between graphene metasurfaces with square patterns performs a maximum 35-fold enhancement compared with the sheet counterpart, far exceeding the performance based on asymmetric patterning. The enhanced heat flux is dominated by a different mechanism through excitation and redshift of graphene-surface plasmon polaritons with high in-plane wavevector. The effects of substrate, vacuum-gap distance, and surface-geometry parameters between the two metasurfaces with symmetric pattern are also investigated. This work opens an alternative route to enhance and modulate the metasurface-based radiative heat transfer for efficient thermal-energy management at micro- and nanoscales.