Abstract
Surface plasmons, free-electron collective oscillations in metallic nanostructures, provide abundant routes to manipulate light-electron interactions that can localize light energy and alter electromagnetic field distributions at subwavelength scales. The research field of plasmonics thus integrates nano-photonics with electronics. In contrast, electronics is also entering a new era of spintronics, where spin currents play a central role in driving devices. However, plasmonics and spin-current physics have so far been developed independently. Here we report the generation of spin currents by surface plasmon resonance. Using Au nanoparticles embedded in Pt/BiY(2)Fe(5)O(12) bilayer films, we show that, when the Au nanoparticles fulfill the surface-plasmon-resonance conditions, spin currents are generated across the Pt/BiY(2)Fe(5)O(12) interface. This spin-current generation cannot be explained by conventional heating effects, requiring us to introduce nonequilibrium magnons excited by surface-plasmon-induced evanescent electromagnetic fields in BiY(2)Fe(5)O(12). This plasmonic spin pumping integrates surface plasmons with spin-current physics, opening the door to plasmonic spintronics.