Collective electronic excitations at metal surfaces are well known to play a key role in a wide spectrum of science, ranging from physics and materials science to biology. Here we focus on a theoretical description of the many-body dynamical electronic response of solids, which underlines the existence of various collective electronic excitations at metal surfaces, such as the conventional surface plasmon, multipole plasmons and the recently predicted acoustic surface plasmon. We also review existing calculations, experimental measurements and applications.

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Theory of surface plasmons and surface-plasmon polaritons

http://myweb.clemson.edu/~daw/D_reprints/MatSciRep.v9p251y93.pdf

The embedded-atom method: a review of theory and applications

Introduction. Density Functional Theory. Surface Plasmons. Nonlocal Optics. Nonlinear Optics. Van der Waals Attraction. Electron-Hole Pair Creation. Index.

Electronic Excitations at Metal Surfaces

Structural studies of alkali metal adsorption and coadsorption on metal surfaces

Low-energy EELS investigation of surface electronic excitations on metals

Correlation between electron loss and inverse photoemission measurements of alkali metals on metal surfaces.

Angle resolved inelastic electron scattering has been used to measure the energy and dispersion of the electronic excitations for Na, K, and Cs thin films on Al(111) as a function of thickness. The energy loss spectrum for a two layer film is dominated by a collective excitation similar to that seen for a thick film. This ‘‘surface plasmon’’ mode for a two‐layer film exhibits a negative dispersion even larger than that observed for the thick film, even though the damping is appreciably larger for the thin film. The loss spectra in the submonolayer region are fundamentally different, apparently dominated by single particle excitations. The transition from a single particle to a collective excitation occurs quite abruptly as the second layer begins to form.

Electron loss spectra from thin alkali films on Al(111)

It is shown that in the nonretarded regime, the frequency of the long-wavelength surface plasmon of a free-electron metal is directly related to the overlap of the metal's unperturbed electron density and the normalized, fluctuating potential of the surface plasmon. This result directly expresses the idea that the surface plasmon's frequency depends on the efficiency with which its electric potential energy can be interchanged with electron kinetic energy. It shows that a negative surface-plasmon dispersion coefficient can be interpreted in terms of decreasing overlap of the fluctuating potential and the unperturbed electron density, as the plasmon wave vector increases.

K. D. Tsuei

Papers

Correlation between electron loss and inverse photoemission measurements of alkali metals on metal surfaces.

Electron loss spectra from thin alkali films on Al(111)

Negative surface-plasmon dispersion coefficient: A physically illustrative, exact formula