Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 74: Nanostructures at surfaces: Other

O 74.5: Vortrag

Donnerstag, 25. März 2010, 16:00–16:15, H34

Magnetotransport in anisotropic Pb-films and monolayers — •Daniel Lükermann, Christoph Tegenkamp, and Herbert Pfnür — Uni Hannover, Inst. für Festkörperphysik, Abt. ATMOS

Pb chain structures with strong anisotropic conductance are formed by adsorption of Pb monolayers (ML) on Si(557). In the case of 1.3 ML, even 1D transport is found along the wire’s direction. The perpendicular direction shows localization due to perfect Fermi nesting for the (223) facet orientation. Above 78 K thermal activation annihilates this phase and a refactting transition switches the system back into an anisotropic transport regime.

In order to learn more about the scattering mechanisms magnetotransport measurements have been performed and analysed using the fromalism by Hikami, which allows to deduce inelastic(τ_i), elastic (τ₀) and spin–orbit (τ_so) scattering times . While for multilayers weak localization, i.e. increase of the resistance by contructive interference of elastically backscattered electrons, has been found, the ML phases show weak anti localization. Contrary to the Pb multilayers, spin-orbit coupling is essential for the ML phases. The anisotropy seen by conductivity measurements is nicely reflected by elastic and spin–orbit scattering rates. Interestingly, for 1.3 ML, a strong increase by three orders of magnitude in τ_so is seen in the parallel direction. As judged from ARPES one of the two split-off bands is nested by the modulation of the wires, while the other crosses the Fermi energy, responsible for the high conductance. This would suggest that spin-flip processes are strongly suppressed, in agreement with the magnetotransport data.