Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 59: Poster Session II (Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: arrays; Nanostructures at surfaces: Wires, tubes; Nanostructures at surfaces: Other; Plasmonics and nanooptics; Metal substrates: Epitaxy and growth; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsoprtion of organic / bio molecules; Metal substrates: Adsoprtion of inorganic molecules; Metal substrates: Adsoprtion of O and/or H; Metal substrates: Clean surfaces; Density functional theory and beyond for real materials)
O 59.42: Poster
Wednesday, March 24, 2010, 17:45–20:30, Poster B1
Acoustic surface plasmons on Au(111) and Au(788) — •U. Krieg1, L. Vattuone2, M. Smerieri2, M. Rocca2, H. Pfnür1, and C. Tegenkamp1 — 1Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstrasse 2, D-30167 Hannover, Germany — 2Dipartimento di Fisica and IMEM-CNR, Università di Genova, I-16146 Genova, Italy
The Acoustic Surface Plasmon (ASP), was predicted theoretically long ago but due to its relatively low cross section it eluded observation until it was firstly observed on Be(0001) and eventually also on Cu(111). We show here that the ASP exists also on Au(111) and on its vicinal surface Au(788). The experiment was performed using ELS-LEED which allows for a high momentum resolution and easy investigation of azimuthal anisotropy of Plasmon dispersion. Interestingly, we find for Au(111) two dispersion branches for ASP. One is nearly isotropic in k-space with slope of 3.8 eVÅ, whereas the other has roughly twice the slope and is visible only along the Γ M direction. Although Au(788) exhibits a quasi one-dimensional partially occupied surface state, the plasmonic dispersion for ASP measured here is two-dimensional and even nearly isotropic. The periodic step structure, however, leads to strong Umklapp scattering so that the multiple branches seen here can actually all be derived from only one dispersing ASP. These results will be discussed taking into account the Rashba split surface bands as well as the role of the reconstruction on flat and regularly stepped Au surfaces. Theoretical ab initio calculations are needed to achieve a full understanding of this complex behaviour.