Nanoscale electromagnetism with the boundary element method

In Yang et al. [Nature 576, 248 (2019)], the authors introduced a general theoretical framework for nanoscale electromagnetism based on Feibelman parameters. Here quantum effects of optically excited electrons at interface between two materials are lumped into complex-valued and frequency-dependent parameters, which can be incorporated modified boundary conditions Maxwell's equations, so-called mesoscopic conditions. These modifications in principle implemeted any Maxwell solver, although technicalities subtle depend chosen computational approach. this paper we show how to implement element method approach, Galerkin scheme with Raviart-Thomas shape elements representation tangential electromagnetic fields boundary. We demonstrate that results our simulations perfect agreement Mie theory including typical simulation scenarios overhead is usually small.