Tuning of magnetosplamon coupling between graphene scatterers for the optimal design of adjustable metasurfaces

Abstract

The resonance characteristics of magnetically-biased graphene micro-scatterers are thoroughly investigated in the present work using both eigenvalue and full-wave solvers. Initially, the graphene surface conductivity is presented in a tensor form due to the application of a magnetostatic bias field, which is perpendicular to the material’s surface. Then, the simple case of a graphene disk scatterer is examined, and a properly modified eigenvalue formulation is utilized to extract the plasmonic fundamental frequencies. The validity of the modal analysis is verified via a full-wave analysis that involves a plane-wave propagation and the extraction of the subsequent absorption cross-section utilizing the Finite-Difference Time-Domain method. Additionally, the dependence of a single disk scatterer resonances with the magnetostatic bias is evaluated, highlighting that as the bias field is increased, every edge mode degenerates into two sub-modes with an augmented difference between the resonant frequencies. Finally, the plasmonic coupling between adjacent scatterers is studied considering a periodic arrangement, similar to a metasurface, indicating the additional coupling modes as well as the adjustability of the properties with multiple degrees of freedom.