Internal Symmetry-Driven Modal Convergence Enhances Chiral Scattering

Chiral scattering in nanostructures emerges from interference between electric and magnetic modes, yet its associated modal strength, arrangements and spectral concentration cannot be inferred from structural handedness alone. Using plasmonic nanorod dimers as a model system, we combine full-field electromagnetic simulations and single-particle circular differential scattering (CDS) spectroscopy to reveal how rotational and translational reconfigurations reshape modal overlap, coupling, and spectral organization even within an established handed architecture. We show that rotational asymmetry tunes the balance between electric-dipole (ED)- and magnetic-dipole (MD)-dominant chiral modes, while translational asymmetry controls their spectral separation and convergence. Consequently, the center-edge configuration produces enhanced and spectrally concentrated CDS responses coinciding with reduced chiral mode splitting and strengthened ED–MD coupling, a mode convergence regime supported both theoretically and experimentally. These results establish modal convergence as a design criterion for tailoring mode organization and scattering through internal symmetry in chiral nanophotonic systems.