Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 46: Electronic Structure of Surfaces: Spectroscopy, Surface States
O 46.4: Poster
Dienstag, 21. März 2017, 18:30–20:30, P1A
Spin-polarized surface states of Pb monolayers on Si(111) — Christian Brand1, Herbert Pfnür1, Jan-Hugo Dil2,3, Stefan Muff2,3, Michael C. Tringides4, and •Christoph Tegenkamp1 — 1Leibniz Universität Hannover, Germany — 2Swiss Light Source, Villigen, Switzerland — 3École Polytechnique Fédérale de Lausanne, Switzerland — 4Ames Laboratory & Iowa State University, Ames, USA
Atomic monolayers (ML) of Pb/Si(111) have recently been found to be superconducting below TC ≈ 1.8 K, but the mechanism behind the evolution of these 2d states is not understood yet. In the range from 6/5 ML to 4/3 ML supercells consisting of linear combinations of (√7 × √3) and (√3 × √3) unit cells are formed (so-called Devil’s staircase regime). This allows us to tune the spin-orbit interaction (SOI), the electronic and atomic structure via adsorption of minute amounts of Pb. In this study we present STM and (SR)-ARPES measurements at low T (> TC) to evaluate the influence of the SOI on the Pb surface states. As it turns out the local adsorption geometry and symmetry of the atomic structure plays an important role for the understanding of the measured spin-polarization by SR-ARPES showing strongly spin-polarized metallic surface states. The experimental results are in very good agreement with DFT calculations and reveal beside a complex spin-texture at EF large Rashba- and Zeeman-type spin-splittings of the Pb surface states.