Subradiant Plasmon Modes in Multilayer Metal-Dielectric Nanoshells

Subradiant plasmon modes play an important role in plasmon coupling, which can couple to the superradiant modes resulting in Fano resonances. In this study, we investigated the behaviors of the subradiant plasmons in multilayer metal-dielectric nanoshells using the generalized Mie theory. We showed that it is possible to get a pronounced Fano resonance in a single concentric nanoshell by controlling the size and geometry. The near-field coupling effects in multilayer nanoshell chains were studied by changing the alignment, particle number, and interparticle spacing. The local electric field and induced surface charge distributions were plotted to gain physical insight into the coupling mechanisms. The interactions between the particles result in a well-developed Fano resonance due to the broadening of bright plasmon modes. The subradiant plasmon modes remain robust and nearly uninfluenced by the near-field coupling and the surrounding medium. At the Fano resonance frequency, the largest field enhancement occurs in the silica layer, which is quite different from solid metal nanoparticle chains.