Bulk plasmons in elemental metals

Abstract

The spectral properties, momentum dispersion, and broadening of bulk plasmonic excitations of 26 elemental metals are studied from first principles calculations in the random-phase approximation. Spectral band structures are constructed from the resulting momentum- and frequency-dependent inverse dielectric function. We develop an effective analytical representation of the main collective excitations in the dielectric response, extending our earlier model based on multipole-Pad\'e approximants (MPAs) to incorporate both momentum and frequency dependence [MPA($\q$)]. With this representation, we identify plasmonic quasiparticle dispersions exhibiting complex features, including non-parabolic energy and intensity dispersions, discontinuities due to anisotropy, and overlapping effects that lead to band crossings and anti-crossings. Comparing with available experimental data, mainly in the optical limit, we find good agreement with the computed spectra. The results for elemental metals and their effective MPA($\q$) representation establish a reference point that can guide both fundamental studies and practical applications in plasmonics and spectroscopy.