FDTD-Compatible broadband surface impedance boundary conditions for graphene

Graphene is a material that has been the focus of much academic interest for its unique material properties. As understanding of graphene improves and fabrication of graphene based devices matures, there is a growing need for electromagnetic simulations of graphene to aid device design. A finite-difference time domain (FDTD) model of graphene is useful for characterizing relevant geometries over a wide range of frequencies, yet limited by the excessive computational resources needed to model this essentially two-dimensional lossy, dispersive medium. A natural alternative is the use of a broadband surface impedance boundary condition (SIBC) that includes both the inter and the intraband conductivity of graphene. This SIBC is developed using a vector-fitting extracted rational function expansion of graphene's surface conductivity, mapped into the time-domain and implemented as a system of field update equations.