Electron emission in the near-field of surface plasmons

Plasmon-enhanced photoelectron emission in the near-field region of gold nanostructures is reported. We show that, depending on the photon energy of the excitation light, the emission from the near-field region can be markedly stronger than from the plasmonic gold itself. Photoemission micrographs also indicate that the spatial confinement of the near-field emission is stronger than in the gold and that the near-field emission exhibits a strong sensitivity on the linear and circular polarization state of the excitation light. The results are explained in terms of work-function differences between the near-field region and the plasmonic material and an interaction between propagating and localized surface plasmon modes. We suggest that the circular polarization sensitivity of the near-field surface plasmon modes may open the way to generate spin-polarized electrons in a plasmon-induced photoemission process.