Surface plasmon polaritons (SPPs) in metallic nanostructures offer new perspectives for integrating optics at the nanoscale. In particular, SPPs provide new methods for the transfer of information and energy at dimensions below the diffraction limit. Excitation of such SPPs on noble metal nanostructures is usually produced by using photon excitation. However, electrical excitation of surface plasmons would have a range of promises for combining nanoelectronics with nanophotonics.

            We will demonstrate that electrical excitation of surface plasmons by using the tip of a  scanning tunneling microscope (STM) enables to produce SPPs with specific properties, (i) a very local electronic excitation, (ii) a 2D circular symmetry, (iii) a broad energy distribution, and (iv) a combination of localized and propagating surface plasmons that depends on the STM tip structure and composition.