A generalized non-local optical response theory for plasmonic nanostructures

• Published in: Nature communications Vol. 5; no. 1; p. 3809
• Main Authors: Mortensen, N. A., Raza, S., Wubs, M., Søndergaard, T., Bozhevolnyi, S. I.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 02-05-2014; Nature Publishing Group
• Subjects: 639/624/400/1021; 639/766/119; 639/766/483/640; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms4809

Metallic nanostructures exhibit a multitude of optical resonances associated with localized surface plasmon excitations. Recent observations of plasmonic phenomena at the sub-nanometre to atomic scale have stimulated the development of various sophisticated theoretical approaches for their description. Here instead we present a comparatively simple semiclassical generalized non-local optical response theory that unifies quantum pressure convection effects and induced charge diffusion kinetics, with a concomitant complex-valued generalized non-local optical response parameter. Our theory explains surprisingly well both the frequency shifts and size-dependent damping in individual metallic nanoparticles as well as the observed broadening of the crossover regime from bonding-dipole plasmons to charge-transfer plasmons in metal nanoparticle dimers, thus unravelling a classical broadening mechanism that even dominates the widely anticipated short circuiting by quantum tunnelling. We anticipate that our theory can be successfully applied in plasmonics to a wide class of conducting media, including doped semiconductors and low-dimensional materials such as graphene.
As plasmonic structures shrink towards sub-nanometre scales, it becomes more important to develop theoretical tools to explain their optical properties. Towards this aim, the authors present a semiclassical approach to describe experimental results for the non-local optical response of nanostructures.