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O: Fachverband Oberflächenphysik

O 15: Spin-Orbit Interaction at Surfaces II

O 15.3: Vortrag

Montag, 22. März 2010, 15:30–15:45, H38

Structural Influence on the Rashba-type Spin-Splitting in Surface Alloys — •Christian R. Ast¹, Isabella Gierz¹, Benjamin Stadtmüller^1,2, Johannes Vuorinen³, Matti Lindroos³, Hugo Dil⁴, Fabian Meier⁴, and Klaus Kern¹ — ¹MPI für Festkörperforschung, Stuttgart — ²Exp. Physik II, Universität Würzburg — ³Tampere University of Technology, Dept. of Physics, Tampere, Finland — ⁴PSI, SLS, Villigen, Switzerland

The Rashba-Bychkov (RB) model has been remarkably successful in describing the spin splitting of two-dimensional (2D) electron systems with a structural inversion asymmetry (SIA). It explains how the spin-degeneracy is lifted by an electric field perpendicular to a 2D free electron system. Looking in more detail, different contributions to a strong spin-splitting at surfaces include a strong atomic spin-orbit interaction, orbital character, a SIA as well as other structural modifications. For surface states, the RB effect can only serve as a qualitative model, because it only accounts for an effective electric field. A number of surface alloys (Bi/Ag(111), Pb/Ag(111), etc.) have been identified with an extremely large spin-split surface state. Interestingly, only a fraction of the atoms at the surface feature a sizeable atomic spin-orbit coupling so that the source of the large spin-splitting must be sought in the structure. We present a systematic study of the alloy atom relaxation in different Ag(111) surface alloys using quantitative low-energy electron diffraction (IV-LEED) measurements and calculations. We relate the alloy atom relaxation to the size of the spin-splitting and discuss possible scenarios of the underlying mechanism.