Plexcitonic dynamics in plasmonic nanorod dimer strongly coupled to a single quantum dot via modulation of dark modes

Strong light-matter interaction in plexcitonic systems plays a crucial role in both fundamental quantum optics study and practical applications, including quantum information processing and nanophotonic devices. However, despite strong light confinement associated with plasmons, large damping of plasmonic cavities remains a major obstacle to achieving strong coupling, particularly with single exciton. Here, we introduce a novel platform that achieves strong coupling via leveraging dark plasmon mode to reduce the loss of the system rather than only enhancing the coupling strength to overcome the system's large damping. Optical properties of the bright/dark modes supported by different silver nanorod dimers are studied, revealing the connection between symmetric configurations and the properties of these resonant modes. The dark mode of side-by-side silver nanorod dimer exhibits an ultralow loss of approximately 22 meV, dramatically decreasing the harsh requirement in coupling strength and enabling strong coupling with a single quantum dot. The time-domain and frequency-domain characteristics of the bright/dark mode-exciton coupling system are compared in detail. Furthermore, a new scheme based on symmetry breaking is proposed to realize the coupling state control across three coupling regimes with different time-domain and frequency-domain characteristics.