Modification of hot carrier spectra in plasmon-molecule systems by optoelectronic strong coupling

Tomasz J. Antosiewicz University of Warsaw

Metallic nanoparticles support plasmon resonances with ultra-small mode volumes and strongly enhanced electric fields which amplify light-matter interactions [1]. We employ real-time TD-DFT simulations to study optoelectronic strong coupling (SC) of magnesium nanoparticles to organic molecules to investigate and focus on two aspects of this interaction.

We quantify, how macroscopic observables, i.e. as given by the coupled oscillators model, originate from microscopic changes visible on the level of single Kohn-Sham transitions and their energy shifts [2]. These changes are the result of modifications of the molecular oscillator in SC systems, such as the resonance energy redshift, Fig. 1a. They correspond to molecular absorption changes, which are attributed to purely molecular transitions coupling to the many nanoparticle energy states, forming mixed transitions, Fig. 1b. These euects can tailor the polaritonic states and ware crucial for novel devices based on SC. Importantly, these changes modify hot carrier dynamics in the upper and lower polariton branches, which can be tuned via the interacting entities, their coupling strength or number. Figure 1c-h shows hot carriers in a SC Mg– CPDT-molecule system [3], where we demonstrate the existence of a SC-mediated charge transfer plasmon whose direction, magnitude, and spectral position can be tuned. We find that the orientation of CPDT changes the nanoparticle–molecule gap for which maximum charge separation occurs, while larger gaps result in trapping hot carriers within the moieties due to weaker interactions. This research highlights the potential for tuning hot carrier generation in strongly coupled plasmon–molecule systems for enhanced energy generation or excited state chemistry.

[1] K. Kluczyk-Korch, T.J. Antosiewicz, Nanophotonics 12, 1711 (2023).

[2] M. Bancerek, J. Fojt, P. Erhart, T.J. Antosiewicz, J. Phys. Chem. C 128, 9749 (2024) [3] R. Zaier, M. Bancerek, K. Kluczyk-Korch, TJ. Antosiewicz, Nanoscale, 16, 12163 (2024)