Optical response of threaded chain plasmons: From capacitive chains to continuous nanorods

We present a detailed theoretical analysis of the optical response of threaded plasmonic nanoparticle strings, chains of metallic nanoparticles connected by cylindrical metallic bridges (threads), based on full-electrodynamic calculations. The extinction spectra of these complex metallic nanostructures are dominated by large resonances in the near infrared, which are associated with charge transfer along the entire string. By analysing contour plots of the electric field amplitude and phase we show that such strings can be interpreted as an intermediate situation between metallic nanoparticle chains and metallic nanorods, exhibiting characteristics of both. Modifying the dielectric environment, the number of nanoparticles within the strings, and the dimensions of the threads, allows for tuning the optical response of the strings within a very broad region in the visible and near infrared.