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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)

O 36.101: Poster

Tuesday, March 15, 2011, 18:30–22:00, P4

Collective electron excitations on potassium-covered Be(0001) — •Martin Jahn and Jörg Kröger — Institut für Physik, TU Ilmenau, PF 100565, DE-98684 Ilmenau, Germany

Electron-energy-loss spectroscopy (EELS) of clean Be(0001) demonstrated the existence of acoustic surface plasmons in agreement with ab initio calculations [1]. The origin of these low-energy collective excitations with a soundlike dispersion relation is the dynamical screening of surface state electrons by bulk electrons. Calculations and photoemission experiments showed that on potassium-covered Be(0001) the interaction of quantum well states with bulk electrons results in coverage-dependent acoustic surface plasmons [2]. We report on EELS measurements on potassium-covered Be(0001). The dispersion relation of the acoustic surface plasmon depending on the potassium coverage is presented. Furthermore, the influence of potassium adsorption on the ordinary surface plasmon and on the phonons of Be(0001) is investigated.

[1] B. Diaconescu et al., Nature 448, 57 (2007).

[2] J. Algdal et al., Phys. Rev. B 78, 085102 (2008).