Optical characterization of charge transfer and bonding dimer plasmons in linked interparticle gaps

We present a theoretical study of the optical properties of nanoparticle dimers connected by conductive gap linkers. The geometrical and conductive properties of the linker modify strongly the optical response of the linked metallic cavity. Two plasmonic modes are responsible for the main spectral features of the cavity: a bonding dimer plasmon (BDP) and a charge transfer plasmon (CTP). We first explore how these two modes are modified as a function of the geometry and the conductance through the cavity, identifying the spatial distribution of the linking current densities. Furthermore, we introduce a resonant feature in the conductivity of the linker, where we observe a complex splitting of the plasmon modes. We also study the capabilities of the BDP and CTP modes in localized surface plasmon resonance (LSPR) sensing.