Plasmonic nanostructures: local versus nonlocal response

Unusual resonances in nanoplasmonic structures due to nonlocal response

“…We have shown that plasmonic nanostructures exhibit unique resonances due to nonlocal response in the hydrodynamic Drude model, but only above the plasma frequency. The recently reported nonlocal resonances in the visible [14][15][16][17][18] agree with older work, 27 but are a surprisingly pronounced consequence of an implementation of the quasistatic approximation that is not self-consistent. For nanowires, we find extinction resonances without making the quasistatic approximation that agree with the quasistatic modes of Ref.…”

“…13 the same nonlocal model was used as in Refs. [14][15][16][17][18], and yet no corresponding modes were found at visible frequencies. Resolving this issue is important for the engineering of ultrasmall plasmonic structures with optimized functionalities.…”

“…This regime challenges the existing theoretical framework resting on a local-response picture using bulk-material parameters. In tiny metallic nanostructures, quantum confinement [3][4][5][6][7] and nonlocal response [8][9][10][11][12][13][14][15][16][17][18] are believed to change the collective plasmonic behavior with resulting strong optical fingerprints and far-reaching consequences for, e.g., field enhancement and extinction cross sections. Within nonlocal response, Maxwell's constitutive relation between the displacement and the electric fields reads D(r,ω) = ε 0 d r ε(r,r ,ω) · E(r ,ω).…”

“…Recent theoretical studies of nanoscale plasmonic structures have predicted considerable differences in the field distributions and scattering cross sections between local and nonlocal response theories, both in numerical implementations of a simplified hydrodynamic Drude model, [14][15][16][17][18] and in corresponding analytical calculations. 15 Importantly, additional resonances of the free-electron plasma were found, also at optical frequencies, which have no counterparts in local-response theories.…”

“…27, and recently in plasmonics by McMahon et al [14][15][16][17] and also by ourselves. 18 Finally, by assumingL J = 0 in the hydrodynamic treatment (3a), the familiar local model is obtained, with J and E related by Ohm's law.…”