Collective Plasmonic-Molecular Modes in the Strong Coupling Regime

TL;DR

This paper demonstrates strong coupling between molecular excited states and surface plasmon modes, revealing new hybrid modes and energy gaps due to long-range molecular interactions mediated by plasmons.

Contribution

It introduces the observation of a new molecular-like mode emerging in the strong coupling regime, attributed to plasmon-mediated long-range molecular interactions.

Findings

Observation of anti-crossing behavior indicating strong coupling

Emergence of a new molecular-like mode with increasing coupling strength

Opening of energy gaps around the free molecule energy level

Abstract

We demonstrate strong coupling between molecular excited states and surface plasmon modes of a slit array in a thin metal film. The coupling manifests itself as an anti-crossing behavior of the two newly formed polaritons. As the coupling strength grows, a new mode emerges, which is attributed to long range molecular interactions mediated by the plasmonic field. The new, molecular-like mode repels the polariton states, and leads to an opening of energy gaps both below and above the asymptotic free molecule energy.