Retardation-effect-induced plasmon modes in a silica-core gold-shell nanocylinder pair

The retardation-effect-induced plasmon modes in a silica-core gold-shell nanocylinder pair is investigated by the two-dimension finite difference time domain method. We show that for light polarized perpendicular to the axis connecting the pair, the spectrum depends sensitively on the size of nanocylinder pair. As the size increases, several retardation-induced non-dipolar plasmon modes including multipolar modes appear in the spectrum and the resonance wavelength and strength of its plasmon modes can be tuned by changing separation width between the nanocylinder pair. Both extinction spectra as a function of size of the core-shell nanocylinder and near-field intensity associated with the coupling resonance modes are reported.