Nonlocal effects in the plasmons of nanowires and nanocavities excited by fast electron beams

The solutions of surface modes in cylindrical metallic wires and cavities are obtained within a nonlocal dielectric formalism. We compare the results with those obtained from standard local approaches. The specular reflection model is applied to describe the nonlocal potentials in the vicinity of the wires and cavities. The external probe exciting the surface plasmons are fast electron beams traveling parallel to the wires and cavities, as those commonly used in electron microscopy and cathodoluminescence. Energy-loss spectra due to surface-plasmon excitation are calculated with use of the nonlocal formalism both for electron trajectories near a metallic nanowire and a metallic nanocavity. When nonlocal effects are considered, the intensity of the plasmon excitation is reduced, and a blueshift of the energy is observed. This effect is more pronounced for very thin wires and cavities where the cylindrical interfaces are strongly interacting. The blueshifts reported here are important for the accurate design of the plasmon response in one-dimensional metallic nanostructures.