Kirsten Andersen, Karsten W. Jacobsen, Kristian S. Thygesen
Electron energy loss spectroscopy (EELS) can be used to probe plasmon excitations in nanostructured materials with atomic-scale spatial resolution. For structures smaller than a few nanometers quantum effects are expected to be important, limiting the validity of widely used semi-classical response models. Here we present a method to identify and compute spatially resolved plasmon modes from first principles based on a spectral analysis of the dynamical dielectric function. As an example we calculate the plasmon modes of 0.5-4 nm thick Na films and find that they can be classified as (conventional) surface modes, sub-surface modes, and a discrete set of bulk modes resembling standing waves across the film. We find clear effects of both quantum confinement and non-local response. The quantum plasmon modes provide an intuitive picture of collective excitations of confined electron systems and offer a clear interpretation of spatially resolved EELS spectra.
View original:
http://arxiv.org/abs/1301.0184
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