  Quantum effects play a significant role in nanometric plasmonic devices, such
as small metal clusters and metallic nanoshells. For structures containing a
large number of electrons, ab-initio methods such as the time-dependent density
functional theory (TD-DFT) are often impractical because of severe
computational constraints. Quantum hydrodynamics (QHD) offers a valuable
alternative by representing the electron population as a continuous fluid
medium evolving under the action of the self-consistent and external fields.
Although relatively simple, QHD can incorporate quantum and nonlinear effects,
nonlocal effects such as the electron spillout, as well as exchange and
correlations. Here, we show an application of the QHD methods to the plasmonic
breathing oscillations in metallic nanoshells. We illustrate the main
advantages of this approach by comparing systematically the QHD results with
those obtained with a TD-DFT code.
