Joint work with Dionisios Margetis (University of Maryland) and Mitchell Luskin (University of Minnesota). The electric conductivity of atomically thick materials such as graphene and black phosphorous yields an effective complex permittivity with a negative real part in the infrared spectrum. This feature allows for the propagation of slowly decaying electromagnetic waves, called surface plasmons-polaritons (SPPs), that are confined near the material interface with wavelengths much shorter than the wavelength of the free-space radiation. In this talk we present a finite element approach for the simulation of SPP structures on a conducting sheet, excited by a plane-wave or electric Hertzian dipole sources. Corresponding analytical results are briefly discussed as well.