Vibrations of weakly-coupled nanoparticles

TL;DR

This paper investigates the vibrational modes of weakly and strongly coupled nanoparticle dimers, revealing how coupling strength influences eigenmodes and frequencies, with implications for optical detection methods.

Contribution

It introduces a combined continuum elasticity and perturbation theory approach to analyze nanoparticle dimers, highlighting the sensitivity of vibrational modes to coupling strength and providing a framework for experimental detection.

Findings

Eigenmodes of dimers are constructed from isolated sphere modes.

Vibrational frequencies are highly sensitive to coupling strength.

Some modes are detectable via inelastic light scattering.

Abstract

The vibrations of a coupled pair of isotropic silver spheres are investigated and compared with the vibrations of the single isolated spheres. Situations of both strong coupling and also weak coupling are investigated using continuum elasticity and perturbation theory. The numerical calculation of the eigenmodes of such dimers is augmented with a symmetry analysis. This checks the convergence and applicability of the numerical method and shows how the eigenmodes of the dimer are constructed from those of the isolated spheres. The frequencies of the lowest frequency vibrations of such dimers are shown to be very sensitive to the strength of the coupling between the spheres. Some of these modes can be detected by inelastic light scattering and time-resolved optical measurements which provides a convenient way to study the nature of the mechanical coupling in dimers of micro and nanoparticles.