Sodium metals for single emitter strong coupling: Alternative plasmonic candidates beyond noble metals

This work provides a theoretical investigation into the strong coupling between a single quantum emitter (QE) and the surface plasmons of sodium metals in two representative plasmonic systems, i.e., the semi-infinite metal-dielectric interface and the metal nanoparticles (NPs) of monomer/dimer configuration. In both configurations, sodium metals exhibit distinctly stronger coupling strength and lower optical loss in the optical region than their noble metal counterparts, demonstrating the ideal candidate characteristics for single-molecule-level strong couplings with distinctly facile operation conditions. Our results provide new insights into extreme light-matter interactions with potential applications in quantum information, optical sensors, quantum chemistry, etc.