  Hot carriers produced from the decay of localized surface plasmons in
metallic nanoparticles are intensely studied because of their optoelectronic,
photovoltaic and photocatalytic applications. From a classical perspective,
plasmons are coherent oscillations of the electrons in the nanoparticle, but
their quantized nature comes to the fore in the novel field of quantum
plasmonics. In this work, we introduce a quantum-mechanical material-specific
approach for describing the decay of single quantized plasmons into hot
electrons and holes. We find that hot carrier generation rates differ
significantly from semiclassical predictions. We also investigate the decay of
excitations without plasmonic character and show that their hot carrier rates
are comparable to those from the decay of plasmonic excitations for small
nanoparticles. Our study provides a rigorous and general foundation for further
development of plasmonic hot carrier studies in the plasmonic regime required
for the design of ultrasmall devices.
