Dimers of Plasmonic Nanocubes to Reach Single-Molecule Strong Coupling with High Emission Yields

Reaching reproducible strong coupling between a quantum emitter and a plasmonic resonator at room temperature, while maintaining high emission yields, would make quantum information processing with light possible outside of cryogenic conditions. We theoretically propose to exploit the high local curvatures at the tips of plasmonic nanocubes to reach Purcell factors of >106 at visible frequencies, rendering single-molecule strong coupling more easily accessible than with the faceted spherical nanoparticles used in recent experimental demonstrations. In the case of gold nanocube dimers, we highlight a trade-off between coupling strength and emission yield that depends on the nanocube size. Electrodynamic simulations on silver nanostructures are performed using a realistic dielectric constant, as confirmed by scattering spectroscopy performed on single nanocubes. Dimers of silver nanocubes feature Purcell factors similar to those of gold while allowing emission yields of >60%, thus providing design rules for efficient strongly coupled hybrid nanostructures at room temperature.