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DS: Fachverband Dünne Schichten

DS 45: Poster IV: One-Dimensional Metals: Reality or Fiction

DS 45.25: Poster

Thursday, April 3, 2014, 16:00–19:00, P1

Plasmonic excitations in Au quantum wires on Ge(001) — •Timo Lichtenstein, Heiko Teiken, Christoph Tegenkamp, and Herbert Pfnür — Leibniz Universität Hannover, Institut für Festkörperphysik, Abteilung ATMOS, 30167 Hannover

One dimensional electronic systems show exceptional transport properties such as Peierl’s transitions or Tomonaga-Luttinger liquid behavior. The latter has been found in Au quantum wires on Ge(001). Their plasmonic excitations should feature a dispersion relation different from the well-known characteristics in two or three dimensions.

Ge substrate preparation was done ex-situ via chemical etching and in-situ by heating to 900 K in a UHV chamber with a base pressure of 7× 10⁻¹¹ mbar. The wires were then formed by evaporation of different amounts of Au at 720 K via self-assembly. The sample quality was controlled with SPA-LEED. Finally, the plasmon dispersion was investigated via EELS combined with a SPA-LEED setup providing both high energy and momentum resolution.

For Au coverages higher than 0.7 ML low-dimensional plasmon modes appear in the loss spectra. Their dispersion relation increases linearly for parallel momentum k_|| > 0.1 Å⁻¹, but significantly deviates from the known dispersion of a quasi one-dimensional plasmon for k_|| < 0.1 Å⁻¹. A contribution coming from Au clusters seen in SEM can be excluded as the FWHM in the loss spectrum decreases steadily with decreasing k_||. A dipole excitation can also be ruled out since it would be observable down to zero momentum.