Plasmon hybridization and the charge-transfer plasmon in a nanoparticle complex: An equivalent circuit model approach
Phys. Rev. A 112, 013521 – Published 17 July, 2025
DOI: https://doi.org/10.1103/p6pq-lhw1
Abstract
The coupling among plasmonic excitations of the nanoparticle complex plays an important role in the responses of optical nanocircuits with multifunction in signal processing. We develop an equivalent circuit model based on the loop matrix method to explore the coupling effects in the complex of nanorods. Our analytical results supported by finite-difference time-domain simulations not only give the resonance characters of (screening) bonding mode, antibonding mode, and charge-transfer plasmon (CTP) mode simultaneously, but also reveal the physics picture of the screening bonding dipole plasmon (BDP) and CTP with common origin (the remnants of multipole plasmonic modes). It is found that the resonance wavelength of the CTP depends sensitively on the length of the conductive bridge connecting the nanorods, showing factor 10 enhancement of measurement (of the interparticle gap size) sensitivity as a nanoruler compared with that based on the BDP, while with changing the bridge width there is a switch of the mode nature with associated change of far-field scattering patterns. In addition, interparticle coupling induced Rabi splitting, Fano effect, and dual CTPs have been found. Our studies provide a new analytical perspective on the electromagnetic coupling mechanism of nanocomposites and establish a foundation for the design of nanocircuits and micro-nano-optical devices.
