Revisiting strong coupling between a single molecule and surface plasmons

Area of Science:

• Plasmonics
• Single-molecule spectroscopy
• Quantum optics

Background:

• Strong coupling between single molecules and plasmons is crucial for sensing and quantum information.
• Understanding the role of metal response (local vs. nonlocal) is key to optimizing this interaction.

Purpose of the Study:

• To reexamine strong coupling between single molecules and surface plasmons using a microscopic classical formulation.
• To investigate the influence of local and nonlocal metal responses on molecule-plasmon coupling.
• To determine conditions for achieving Rabi splitting without a resonator.

Main Methods:

• Microscopic classical formulation of molecule-plasmon interaction.
• Analysis of local and nonlocal responses of metallic nanoparticles (silver).
• Investigation of molecule-metal separation and dielectric function effects.

Main Results:

• Strong molecule-plasmon coupling observed in the UV range for silver nanoparticles with molecule-metal separation ≤ 1 nm (local response).
• Nonlocal response consideration shifts strong coupling to even shorter molecule-metal distances.
• Rabi splitting demonstrated without the need for a plasmonic resonator.

Conclusions:

• Achieving strong molecule-plasmon coupling and Rabi splitting is feasible with optimized nanoparticle geometry and proximity.
• The study provides a classical framework for understanding quantum phenomena in plasmonic systems.
• This work has implications for designing advanced nanoscale devices for spectroscopy and quantum applications.