Space-domain method of moments for graphene nanoribbons

A space-domain formulation of the method of moments is presented for the modal analysis of graphene nanoribbons (GNRs). Starting from a full spectral representation of graphene conductivity, recently obtained in a semiclassical framework using the Bhatnagar-Gross-Krook approximation of the Boltzmann transport equation, an approximate spacedomain integro-differential equation is derived for the current density on a GNR, valid in the limit of low wavenumbers. The equation is then discretized with the method of moments adopting subsectional basis functions and enforcing the correct behavior of the transverse current at the edges. The resulting formulation allows for an effective treatment of both single and multiple GNRs as well as for inclusion of a spatially varying carrier density. Comparisons are presented with results obtained with an in-house code based on a spectral-domain formulation that incorporates exactly the effect of edges within the nonlocal graphene model.