Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 12: Nanostructures at Surfaces II (Wires, Tubes)
O 12.2: Vortrag
Montag, 26. März 2007, 14:30–14:45, H36
Switching between 1d and 2d by complete and incomplete Fermi nesting in Pb chains grown on Si(557) — •C. Tegenkamp1, H. Pfnür1, T. Ohta2, J.L. McChesney2, E. Rotenberg2, and K. Horn3 — 1Institut für Festkörperphysik, Leibniz-Universität Hannover, 30167 Hannover, Germany — 2ALS, Lawrence Berkley National Laboratory, Berkley, CA. 94720, USA — 3FHI der Max-Planck Gesellschaft, 14195 Berlin, Germany
As shown recently by STM and LEED, the adsorption of 1ML Pb at low temperatures on Si(557) followed by annealing to 640K leads to the formation of Pb-chains with an interachain spacing of d=1.5nm. The closely packed Pb film on the micro-Si(111) facets forms locally a √3 × √3 structure, which shows in addition a 10-fold periodicity along the [1 10] direction. Conductivity measurements below 78K have shown that electronic transport occurs only along the chain direction, whereas insulating behavior is found in the perpendicular direction. Above 78K, the sytsem switches into a 2d-regime, i.e. activated transport is found in both directions. Using angle resolved photoemission (ARPES), we explored the origins of the quasi one-dimensional (1d) conductance found below 78K. The interchain distance is reflected directly by Umklapp structures in the [11 2] direction close to EF. As ARPES reveals further, ordering into the chain structure below 78K results in complete Fermi nesting in the [11 2] direction and in energy reduction by band filling. The domain structure along the chains forms split-off valence bands with mesoscopic λF, responsible for the 1d conductance without further instabilities at low temperatures.