Double Rabi Splitting in a Strongly Coupled System of Core–Shell Au@Ag Nanorods and J‑Aggregates of Multiple Fluorophores

The interaction of several components in the strong coupling regime yielding multiple Rabi splittings opens up remarkable possibilities for studies of multimode hybridization and energy transfer, which is of considerable interest in both fundamental and applied science. Here we demonstrate that three different components, such as core–shell Au@Ag nanorods and J-aggregates of two different dyes, can be integrated into a single hybrid structure, which leads to strong collective exciton–plasmon coupling and double-mode Rabi splitting totaling 338 meV. We demonstrate strong coupling in these multicomponent plexitonic nanostructures by means of magnetic circular dichroism spectroscopy and demonstrate strong magneto-optical activity for the three hybridized states resulting from this coupling. The J-aggregates of two different nonmagnetic dyes interact with metal nanoparticles effectively, achieving magnetic properties due to the hybridization of electronic excitations in the three-component system.