Decay dynamics of Localised Surface Plasmons: damping of coherences and populations of the oscillatory plasmon modes

TL;DR

This paper investigates the decay dynamics of localized surface plasmons in metal nanoparticles, linking classical and quantum descriptions to understand damping processes and how they can be controlled.

Contribution

It introduces a quantum open system approach to distinguish damping of populations and coherences in plasmon modes, independent of nanoparticle size.

Findings

Quantum model separates damping of populations and coherences.

Intrinsic relations between damping rates are established.

Impact of radiative and nonradiative channels is analyzed.

Abstract

Properties of plasmonic materials are associated with surface plasmons - the electromagnetic excitations coupled to coherent electron charge density oscillations on a metal/dielectric interface. Although decay of such oscillations cannot be avoided, there are prospects for controlling plasmon damping dynamics. In spherical metal nanoparticles (MNPs) the basic properties of Localized Surface Plasmons (LSPs) can be controlled with their radius. The present paper handles the link between the size-dependent description of LSP properties derived from the dispersion relation based on Maxwell's equations and the quantum picture in which MNPs are treated as "quasi-particles". Such picture, based on the reduced density-matrix of quantum open systems ruled by the master equation in the Lindblad form, enables to distinguish between damping processes of populations and coherences of multipolar plasmon oscillatory states and to establish the intrinsic relations between the rates of these processes, independently of the size of MNP. The impact of the radiative and the nonradiative energy dissipation channels is discussed.