Collective electronic excitations in a potassium‐covered Be surface

Abstract

We investigate within a two‐component jellium model the collective electronic excitations in a one‐monolayer (1ML) potassium covered beryllium surface. The calculations of the surface dynamical response properties have been performed with one‐particle energies and wave functions derived from the Kohn‐Sham density‐functional theory. The dispersion relation for the surface plasmon modes as well as the real and imaginary parts of the induced dynamical charge density oscillations are presented. Comparison of the collective modes in the 1ML K/Be system with that of a clean Be surface is made. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Modification of response properties of the Be(0001) surface upon adsorption of a potassium monolayer: An ab initio calculation

“…Second, additionally to the Be‐substrate‐originated surface bands, a partly occupied K‐derived energy band residing in a wide projected energy gap around the SBZ center, i.e., a QWS band, appears. This is in stark contrast with the prediction of the jellium model which does not allow selection of any separate quantum state linked to the K monolayer 81. The energy position of this band at the $\overline {\Gamma } $ point and its quasiparabolic dispersion is in good agreement with other ab initio calculation and experimental photoemission data 50.…”

“…from the Be substrate border, i.e., fairly coinciding with the spatial expansion of the QWS charge density 50. In difference to the jellium model predictions 81, at small momenta the ab initio calculation gives the $\omega _{{\rm m}}^{{\rm K}} $ mode as a narrow sharp peak (see Figs. 2 and 4).…”

“…It is interesting to address completely different behavior of $\rho {}^{{\rm ind}} $ in the interior of the Be substrate at energies in vicinity of the Be plasmon energy, $\omega _{{\rm b}}^{{\rm Be}} $ , in comparison with that obtained within the jellium model 81. In particular, instead of strong energy oscillations of $\rho {}^{{\rm ind}} (z,{\bf q}_{||} ,\omega )$ at a given distance z for energies $\omega > \omega _{{\rm b}}^{{\rm Be}} $ in the jellium model, the ab initio $\rho {}^{{\rm ind}} (z,{\bf q}_{||} ,\omega )$ in Figs.…”

Phonon-Induced Surface Charge Density Oscillations in Quantum Wells: A First-Principles Study of the (2 × 2)-K Overlayer on Be(0001)

“…These effects are found to be pronounced in supported metal multilayers characterized by free-electron quantum well (QW) states. , A special case is represented by alkali overlayers, due to their ability in enhancing certain surface reactions and field emission. , On a more fundamental side, in these systems, the coupling of the overlayer phonons to electronic transitions between states of the two-dimensional electron gas (2DEG) allows the study of the effects of a quasi-2D electron−phonon interaction. ,, 2DEG associated with a potassium layer adsorbed on Be(0001) is presently attracting much interest of theoreticians also for the occurrence of collective electronic excitations of acoustic type − and their involvement in photoemission , as a natural follow-up to the recent discovery of surface acoustic plasmons in Be(0001) . The investigation of the surface phonon structure and e-p interaction of K/Be(0001) appears as a necessary complement to these studies.…”