Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 26: Nanostructured Materials I
MM 26.1: Vortrag
Mittwoch, 25. März 2009, 10:15–10:30, IFW B
Photoexcitation of Volume Plasmons in Metallic Nanostructures — •Katja Ehrhold1, Ulrich Gösele1, and Silke Christiansen2,1 — 1Max-Planck-Institut, Weinberg 2, 06120 Halle — 2Institut für Photonische Technologien, Albert-Einstein-Str. 9, 07745 Jena
It has long been known that a vanishing permittivity enables longitudinal electromagnetic waves. The corresponding collective eigenmodes called volume plasmons should not be dipole excitable in classical electrodynamics. Thus, the typical volume modes are known to be excitable via particle beams solely.
We investigated typical scattering problems for an incident plane wave determined via the Helmholtz-equation which can be solved analytically for special geometries. The analytical solution for a spherical scatterer by Gustav Mie was extended to spherical core-shell structures by Aden. Remarkably, in the case of metallic nanoshell structures the Mie extinction efficiencies have a local maximum at the natural plasma frequency corresponding to the photoexcitation of a volume plasmon. This volume mode is independent of both the shell's aspect ratio and the core material. For explanation we present a simple physical picture which is supported by analytical examples on silver and gold shells. Additionally we use finite element simulations to show a potpourri of particles which likewise enable the photoexcitation of volume modes.