Abstract
Plasmon-generated hot carriers are used in photovoltaic or photochemical applications. However, the interplays between the plasmon and single-particle excitations in nanosystems have not been theoretically addressed using ab initio methods. Here we show such interplays in a Ag55 nanocluster using real-time time-dependent density functional theory simulations. We find that the disappearance of the zero-frequency peak in the Fourier transform of the band-to-band transition coefficient is a hallmark of the plasmon. We show the importance of the d-states for hot-carrier generations. If the single-particle d-to-s excitations are resonant to the plasmon frequency, the majority of the plasmon energy will be converted into hot carriers, and the overall hot-carrier generation is enhanced by the plasmon; if such resonance does not exist, we observe an intriguing Rabi oscillation between the plasmon and hot carriers. Phonons play a minor role in plasmonic dynamics in such small systems. This study provides guidance on improving plasmonic applications.
Highlights
Plasmon-generated hot carriers are used in photovoltaic or photochemical applications
For noble-metal nanostructures, the plasmon frequencies, which depend on the size, shape, metal composition and surrounding dielectric environment[6,7], are generally in visible or ultraviolet regions that cover a large portion of the solar spectrum[8]
We find that if the single-particle d-to-s excitations resonant to the plasmon frequency exist, most plasmon energy will be converted into hot carriers, enhancing hot-carrier generations
Summary
Plasmon-generated hot carriers are used in photovoltaic or photochemical applications. The interplays between the plasmon and single-particle excitations in nanosystems have not been theoretically addressed using ab initio methods We show such interplays in a Ag55 nanocluster using real-time time-dependent density functional theory simulations. Those studies treated plasmons classically as oscillating electromagnetic fields, and used the perturbation theory (Fermi’s golden rule) to calculate the hot-carrier generations They did not describe the feedback of hot carriers to plasmons, nor represent the plasmon and singleparticle excitations in a unified quantum mechanical framework. There were rt-TDDFT simulations on nanoclusters up to several hundred atoms using local-orbital basis or real-space grids[28,29] Those works studied only the optical absorption spectra[28,29], instead of the interplays and energy transfers between the plasmon and single-particle excitations. Our recently developed fast rt-TDDFT algorithm[31] enables us to simulate such long time with plane-wave basis sets
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