On the surface impedance modeling of metasurfaces composed of graphene-coated spherical nanoparticles

Abstract

In this paper, we discuss the electromagnetic homogenization of graphene-based nanoparticle arrays using the surface impedance approach. For this purpose, we first investigate the contribution of the different harmonics to the equivalent surface impedance of the array. We conclude that the size of the nanoparticles is small compared to the operating wavelength, and the higher-order modes have a negligible impact on the overall response of the array. Then, the accuracy of the homogenization method to describe the macroscopic response of graphene-coated spherical particle arrays is discussed. In particular, it is demonstrated that the surface-impedance modeling provides reliable results when the level of coupling between the nanoparticles is moderate and the model accuracy can be slightly improved by considering the Floquet expansion-based interaction coefficient. Finally, approximate formulas for the array surface impedance, as well as an equivalent circuit model of the metasurface, are extracted.