Surprises in light scattering by tiny metal nanowires.
Scattering of light by water drops, glass windows, or metal wires is usually well described in terms of their refractive index. Not so for tiny metal nanowires: we predict unusual scattering resonances that the refractive-index description completely misses. Metals are shiny because they contain electrons that are free to move, as the usual Drude model explains. We go one step further and describe the free electrons 'hydrodynamically', as a moving fluid in which the electron density can vary and pressure waves exist, analogous to sound waves. We find that these pressure waves can be excited simply by illuminating a metallic wire with light. In very small wires (diameters comparable to the electronic wavelength, below 10 nanometers), the electrons start to 'feel the walls' and their pressure waves can become standing waves. It is those standing waves that give rise to the unusual resonances in light scattering that we report. The fabrication of nanometer-sized metal structures, such as spheres and wires, is becoming a reality. Our results not only improve our understanding of the fundamental interaction between electrons and light, but also allow us to manipulate and control these new phenomena.
The paper, "Unusual resonances in nanoplasmonic structures due to nonlocal response" in authored by Søren Raza, Giuseppe Toscano, Antti-Pekka Jauho, Martijn Wubs, amd Asger Mortensen.
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