Influence of the electron spill-out and nonlocality on gap plasmons in the limit of vanishing gaps

Abstract

We study the effect of electron spill-out and of nonlocality on the propagation of light inside a gap between two semi-infinite metallic regions. We compare the predictions of a local response model taking into account only the spill-out, to the predictions of a quantum hydrodynamic model able to take both phenomena into account. We show that only the latter is able to correctly retrieve the correct limit when the gap closes, while the local model suffers from undesirable features (divergence of the fields, overestimation of the losses). Finally, we show that, to a certain extent, the correct results can be retrieved using a simple local approach without spill-out or a conventional Thomas-Fermi approximation, but considering an effective gap width.

Second-harmonic generation in plasmonic waveguides with nonlocal response and electron spill-out

“…We compute the space-dependent equilibrium electron density n 0 (r) self-consistently using the zero-th order QHT equation (see Refs. [54,68] for more details). The color map and line plot of n 0 , showing the electron spill-out from the metal-dielectric interface, are presented in Fig.…”

Study of Field Enhancement in the Subnanometer Gap of Plasmonic Dimers Accounting for the Surface Quantum Effect

“…This approach allows one to describe the effect of electron spill-out when electrons leave the metal surface. The spill-out (or spill-in) scale is characterized by the Feibelman d-parameters, the values of which are usually several angstroms [30]. Such a small length scale makes the spill-out effect noticeable only in a nanometer-sized metal particle [31] or a subnanometer gap [32].…”