Strong Plasmon-Exciton Coupling in Colloidal Cubic Nanoparticles and Layered Molecular J-aggregates

Strong coupling between light and matter can lead to the formation of hybrid eigenstates, such as exciton-polaritons, enriching our understanding and manipulation of quantum phenomena across various fields of science and technology. While plasmonic metal nanoparticles are recognized as effective optical resonators for generating polaritons, most research to date has been focused on Au nanorods, and the potential of cubic nanoparticles and the approach of layering emitters on particle surfaces have not been extensively investigated in this field. This paper presents our findings on the strong coupling observed between cubic nanoparticles and molecular J-aggregates. Our results suggest that the coupling strength can be tuned by adjusting the geometric and material properties of the cubic nanoparticles, as evidenced by spectral splitting, anti-crossing in dispersion relations, and the fulfillment of strong coupling criteria. To further enhance plasmon-exciton coupling, we introduced a layer-by-layer modification approach and observed a maximal enhancement of approximately 19% for double layers of J-aggregates. Simulations on the interlayer thickness-dependent splitting enhancement corroborate these results, providing a deeper understanding of the effects of emitter layering on plasmon-exciton strong coupling.