Damping rates of surface plasmons for particles of size from nano- to micrometers; reduction of the nonradiative decay

TL;DR

This paper investigates the damping rates of surface plasmons in gold and silver nanospheres across a wide size range, revealing size-dependent damping behaviors and the impact of interface damping, with implications for resonance quality.

Contribution

The study introduces a classical electrodynamics model incorporating interface damping to explain size-dependent plasmon damping rates and unexpected reductions in certain size ranges.

Findings

Damping rates increase then decrease with particle size.

Interface damping significantly affects smaller particles.

Reduction in damping rates due to suppressed nonradiative decay channels.

Abstract

Damping rates of multipolar, localized surface plasmons (SP) of gold and silver nanospheres of radii up to $1000nm$ were found with the tools of classical electrodynamics. The significant increase in damping rates followed by noteworthy decrease for larger particles takes place along with substantial red-shift of plasmon resonance frequencies as a function of particle size. We also introduced interface damping into our modeling, which substantially modifies the plasmon damping rates of smaller particles. We demonstrate unexpected reduction of the multipolar SP damping rates in certain size ranges. This effect can be explained by the suppression of the nonradiative decay channel as a result of the lost competition with the radiative channel. We show that experimental dipole damping rates [H. Baida, et al., Nano Lett. 9(10) (2009) 3463, and C. S\"onnichsen, et al., Phys. Rev. Lett. 88 (2002) 077402], and the resulting resonance quality factors can be described in a consistent and straightforward way within our modeling extended to particle sizes still unavailable experimentally.