Ultrafast dynamics of plasmons and strong plasmon-molecule coupling at the nanoscale: Insights from first-principles modeling

Localized surface plasmons render metal nanoparticles efficient light absorbers at their resonance frequencies. After light absorption by the plasmon mode, the system can display different femtosecond-scale processes: The plasmon can decay into incoherent electrons and holes or a coherent energy exchange can take place between plasmon and other strongly-coupled electronic excitations. In this presentation, we employ time-dependent density-functional theory (TDDFT) for providing first-principles insights on these ultrafast processes at the nanoscale. We analyze the electron-hole transitions involved in photoabsorption and in the subsequent dynamics of the electronic system, which enables us to scrutinize the plasmonic character [1], follow the plasmon decay into hot electrons and holes [2], and dissect the symmetric and antisymmetric hybrid modes caused by strong coupling between plasmon and molecular excitation [3]. Our work paves the way for addressing spatiotemporal dynamics of plasmon-enhanced processes down to the atomic-scale details.

[1] T. P. Rossi et al., J. Chem. Theory Comput. 13, 4779 (2017).
[2] T. P. Rossi et al. (unpublished).
[3] T. P. Rossi et al., Nat. Commun. 10, 3336 (2019).