Probing plexciton dynamics with higher-order spectroscopy

Area of Science:

• Optics and Photonics
• Materials Science
• Chemical Physics

Background:

• Surface-plasmon polaritons (SPPs) are light modes coupled to electron oscillations on metal surfaces.
• Plexcitons are hybrid quasiparticles formed by coupling molecular excitons to SPPs.
• Plexcitonic systems offer tunable properties for controlling molecular processes.

Purpose of the Study:

• Investigate energy transfer dynamics in a zinc phthalocyanine/SPP plexcitonic system.
• Analyze the influence of exciton-SPP mixing on excitation transport.
• Understand the underlying mechanisms governing energy transfer in these hybrid systems.

Main Methods:

• Utilized higher-order pump-probe spectroscopy to probe two-particle interaction dynamics.
• Varied the angle of incidence to control the degree of exciton-SPP mixing.
• Employed a rate equation model to interpret experimental observations.

Main Results:

• Excitation transport in the plexcitonic system was found to be independent of the exciton-SPP mixing ratio.
• Fifth-order spectroscopy revealed consistent transport dynamics across varying mixing levels.
• A fast transition to localized excitonic dark states was identified as the key mechanism.

Conclusions:

• The transport of energy in plexcitons is primarily governed by transitions to localized excitonic states, not the delocalized plasmon modes.
• Hybrid exciton-plasmon systems require careful design to leverage plasmon delocalization for enhanced transport.
• Findings provide insights into optimizing plexcitonic systems for applications in energy transfer and molecular processes.