title: Correlation-induced double-plasmon excitation in simple metals studied by inelastic x-ray scattering.
abstract: We report a new type of peaklike structure observed in the tail of the dynamic structure factor of simple metals, measured by inelastic x-ray scattering. Based on the momentum-transfer dependence of the energy position and the intensity of this structure, it has been unambiguously attributed to intrinsic plasmon-plasmon excitations, an electronic correlation effect that was theoretically predicted by many-body perturbation theory of the homogeneous-electron-gas model beyond the random-phase approximation. This signature appears to be largely unaffected by electron-ion interaction effects. Thus a structure that is primarily caused by correlation effects in the electron gas has been found experimentally in the dynamic structure factor of simple metals.
authors.affiliation: Institute of Physics, University of Dortmund, D-44221 Dortmund, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Sternemann
authors.forename: S
authors.initials: S
authors.lastname: Huotari
authors.forename: G
authors.initials: G
authors.lastname: Vankó
authors.forename: M
authors.initials: M
authors.lastname: Volmer
authors.forename: G
authors.initials: G
authors.lastname: Monaco
authors.forename: A
authors.initials: A
authors.lastname: Gusarov
authors.forename: H
authors.initials: H
authors.lastname: Lustfeld
authors.forename: K
authors.initials: K
authors.lastname: Sturm
authors.forename: W
authors.initials: W
authors.lastname: Schülke