Field enhancement at metallic interfaces due to quantum confinement

Abstract

We point out an apparently overlooked consequence of the boundary conditions obeyed by the electric displacement vector at air-metal interfaces: the continuity of the normal component combined with the quantum mechanical penetration of the electron gas in the air implies the existence of a surface on which the dielectric function vanishes. This, in turn, leads to an enhancement of the normal component of the total electric field. We study this effect for a planar metal surface, with the inhomogenous electron density accounted for by a Jellium model. We also illustrate the effect for equilateral triangular nanoislands via numerical solutions of the appropriate Maxwell equations, and show that the field enhancement is several orders of magnitude larger than what the conventional theory predicts

Modified field enhancement and extinction by plasmonic nanowire dimers due to nonlocal response

“…In this work we neglected quantum tunneling effects [25,29]. In their quantum many-body calculations, Zuloaga et al [25] identify a cross-over regime for dimer gaps between 0.5 and 1.0 nm, where narrow-barrier quantum tunneling effects strongly reduce the classical hybridization energies, and a conductive regime for d < 0.5 nm.…”

“…As stated in the Introduction, we do not consider the 'spill-out' of the electron density at the metal surface leading to quantum tunneling, as described by microscopic many-body calculations [25,29]. As an immediate consequence of this approximation, the normal component of the current J vanishes at the surface of the metal volume(s).…”

Unusual resonances in nanoplasmonic structures due to nonlocal response

“…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).…”

Perfect imaging, epsilon-near zero phenomena and waveguiding in the scope of nonlocal effects

“…Recent experiments explore this frontier1314151617 that has come into reach for modern nano-fabrication methods. The hydrodynamic approach7181920212223242526 and other semi-classical theories627282930 have proven important for analyzing the observed effects. In the hydrodynamic model, quantifies the strength of the nonlocal response associated with hydrodynamic pressure due to electron-electron interactions, where v F is the material dependent Fermi velocity.…”