Surface-plasmon resonances of arbitrarily shaped nanometallic structures in the small-screening-length limit

TL;DR

This paper develops a perturbation theory to analyze surface-plasmon resonance blueshifts in arbitrarily shaped nanometallic structures due to nonlocal electron response, especially in the small-screening-length limit.

Contribution

It introduces a coarse-grained nonlocal description using matched asymptotic expansions for arbitrary nanostructures, extending understanding of nonlocal effects beyond simple geometries.

Findings

Nonlocal effects cause blueshifts in plasmon resonances.

Eigenfrequencies of nearly touching nanowires are renormalized by nonlocality.

The theory applies to arbitrary shapes in the small-screening-length limit.

Abstract

According to the hydrodynamic Drude model, surface-plasmon resonances of metallic nanostructures blueshift owing to the nonlocal response of the metal's electron gas. The screening length characterising the nonlocal effect is often small relative to the overall dimensions of the metallic structure, which enables us to derive a coarse-grained nonlocal description using matched asymptotic expansions; a perturbation theory for the blueshifts of arbitrary shaped nanometallic structures is then developed. The effect of nonlocality is not always a perturbation and we present a detailed analysis of the "bonding" modes of a dimer of nearly touching nanowires where the leading-order eigenfrequencies and eigenmode distributions are shown to be a renormalisation of those predicted assuming a local metal permittivity.