Field enhancement at metallic interfaces due to quantum confinement

TL;DR

This paper reveals that quantum confinement effects at metallic interfaces cause a significant enhancement of the electric field, surpassing traditional predictions, with implications for nanoplasmonics.

Contribution

It introduces the concept that boundary conditions and quantum electron penetration lead to a vanishing dielectric surface, causing strong field enhancement at metal interfaces.

Findings

Field enhancement is several orders of magnitude larger than conventional theory predicts.

Quantum mechanical effects at interfaces are crucial for accurate electromagnetic modeling.

Numerical simulations confirm the significant impact of quantum confinement on local fields.

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.