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

Abstract

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.

Amplified Plasmonic Forces from DNA Origami-Scaffolded Single Dyes in Nanogaps

“…The interplay of energy between a light emitter and its environment modifies its spontaneous emission rate through the Purcell effect. Placing a quantum emitter in a photonically structured environment such as an optical cavity or photonic crystal can enhance the light–matter interaction enough to enter the strong-coupling regime. − By using metallic nanostructures, light can be even more tightly confined to sub-diffraction-limited gaps, enhancing fluorescence and revealing (ultra)­strong light–matter coupling. − These arise from the localized surface plasmons supported on metal nanostructures, which create tightly confined electromagnetic hot spots. The localized plasmons couple to radiative electronic transitions of any chromophore placed in the proximity, such as dye molecules or semiconductor quantum dots. − , …”