Lifetime of the first and second collective excitations in metallic nanoparticles

TL;DR

This paper investigates the lifetimes of surface plasmons and second collective excitations in metallic nanoparticles, emphasizing Landau damping, electronic confinement effects, and the influence of particle size and shape.

Contribution

It provides a semiclassical analysis of plasmon lifetimes, including oscillating components and the impact of potential shape, and explores the conditions for second excitation resonance.

Findings

Lifetime increases smoothly with particle size

Oscillating component in lifetime due to semiclassical effects

Second excitation remains a well-defined resonance

Abstract

We determine the lifetime of the surface plasmon in metallic nanoparticles under various conditions, concentrating on the Landau damping, which is the dominant mechanism for intermediate-size particles. Besides the main contribution to the lifetime, which smoothly increases with the size of the particle, our semiclassical evaluation yields an additional oscillating component. For the case of noble metal particles embedded in a dielectric medium, it is crucial to consider the details of the electronic confinement; we show that in this case the lifetime is determined by the shape of the self-consistent potential near the surface. Strong enough perturbations may lead to the second collective excitation of the electronic system. We study its lifetime, which is limited by two decay channels: Landau damping and ionization. We determine the size dependence of both contributions and show that the second collective excitation remains as a well defined resonance.