Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance.

A metallic nanostructure consisting of a disk inside a thin ring supports superradiant and very narrow subradiant modes. Symmetry breaking in this structure enables a coupling between plasmon modes of differing multipolar order, resulting in a tunable Fano resonance. The LSPR sensitivities of the subradiant and Fano resonances are predicted to be among the largest yet for individual nanostructures.