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Plasmon-Induced Hot-Carrier Generation differences in Gold and Silver Nanoclusters
preprintsubmitted on 27.03.2019, 23:03 and posted on 28.03.2019, 15:30 by Oscar A. Douglas-Gallardo, Matias Berdakin, Thomas Frauenheim, Cristián G Sánchez
In the last thirty years, the study of plasmonic properties of noble metal nanostructures has become a very dynamic research area. The design and manipulation of matter in the nanometric scale demand a deep understanding of the underlying physico-chemical processes that operate in this size regimen. Here, a fully atomistic study of the spectroscopic and photodynamic properties of different icosahedral silver and gold nanoclusters have been carried out by using Time-Dependent Density Functional Tight-Binding (TD-DFTB) model. Optical absorption spectra of different icosahedral silver and gold nanoclusters of diameters between 1 and 4 nanometers has been simulated. Furthermore, the energy absorption process have been quantified by means of calculating a fully quantum absorption cross-section using the information contained in the reduced single-electron density matrix. This approach allows us take into account for the quantum confinement effects dominating in this size regime. Likewise, the plasmon-induced hot-carrier generation process under laser illuminations have been explored from a fully dynamical perspective. We have found noticeable differences in the energy absorption mechanisms and the plasmon-induced hot-carrier generation process in both metals which can be explained by their respective electronic structures. These difference can be attributed to the existence of ultra-fast electronic dissipation channels in gold nanoclusters that are absented in silver nanoclusters. To the best of our knowledge, this is the first report that addresses this topic from a real time fully atomistic time-dependent approach.