Anomalous plasmon hybridization in nanoantennas near interfaces

We report on an anomalous plasmon hybridization in side-by-side coupled metallic nanoantennas on top of a silicon waveguide. Contrary to the conventional perception based on Coulomb coupling, the hybridized anti-symmetric mode in our structure possesses a higher resonance frequency than the symmetric mode. This unusual phenomenon reveals a new mechanism of plasmon hybridization, namely, coupling-induced charge redistribution. Our work includes numerical simulation, experimental validation, and theoretical analysis, emphasizing the importance of dielectric interfaces in coupled plasmonic structures, and offers new possibilities for non-Hermitian systems and integrated devices.