Time-dependent transport of a localized surface plasmon through a linear array of metal nanoparticles: Precursor and normal mode contributions

TL;DR

This paper theoretically analyzes the time-dependent transport of localized surface plasmons in a linear nanoparticle array, identifying two propagating signals with distinct velocities and decay behaviors, including a novel Sommerfeld-Brillouin precursor.

Contribution

It introduces the identification of a previously unrecognized Sommerfeld-Brillouin precursor in plasmon transport and characterizes its properties in nanoparticle arrays.

Findings

Two signals propagate: one with group velocity and exponential damping.

A second, faster signal with power-law decay dominates at large distances.

The precursor remains confined near the array despite spreading in the propagation direction.

Abstract

We theoretically investigate the time-dependent transport of a localized surface plasmon excitation through a linear array of identical and equidistantly spaced metal nanoparticles. Two different signals propagating through the array are found: one traveling with the group velocity of the surface plasmon polaritons of the system and damped exponentially, and the other running with the speed of light and decaying in a power-~law fashion, as $x^{-1}$ and $x^{-2}$ for the transversal and longitudinal polarizations, respectively. The latter resembles the Sommerfeld-Brillouin forerunner and has not been identified in previous studies. The contribution of this signal dominates the plasmon transport at large distances. In addition, even though this signal is spread in the propagation direction and has the lateral dimension larger than the wavelength, the field profile close to the chain axis does not change with distance, indicating that this part of the signal is confined to the array.