Decay of dark and bright plasmonic modes in a metallic nanoparticle dimer

TL;DR

This paper presents a quantum theory for coupled plasmonic modes in metallic nanoparticle dimers, providing analytical expressions for their frequencies and decay rates, and identifying Landau damping as the main decay channel for dark modes.

Contribution

It introduces a comprehensive quantum framework for analyzing plasmonic mode decay in nanoparticle dimers, including analytical formulas for mode properties.

Findings

Dark plasmonic modes decay mainly via Landau damping.

Bright and dark mode frequencies and decay rates are analytically derived.

Dark modes are weakly coupled to light and resistant to radiation damping.

Abstract

We develop a general quantum theory of the coupled plasmonic modes resulting from the near-field interaction between localized surface plasmons in a heterogeneous metallic nanoparticle dimer. In particular, we provide analytical expressions for the frequencies and decay rates of the bright and dark plasmonic modes. We show that, for sufficiently small nanoparticles, the main decay channel for the dark plasmonic mode, which is weakly coupled to light and, hence, immune to radiation damping, is of nonradiative origin and corresponds to Landau damping, i.e., decay into electron-hole pairs.