Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 48: Focused Session: Spin-Orbit Interaction at Surfafces: From the Rashba Effect to Topological States of Matter I

O 48.6: Talk

Thursday, March 26, 2009, 12:30–12:45, HSZ 02

Rashba effect in unoccupied states: Two-photon photoemission experiments and first-principles calculations for Bi/Cu(111) — Ping Yu, Cheng-Tien Chiang, Aimo Winkelmann, Hossein Mirhosseini, Arthur Ernst, Sergey Ostanin, •Jürgen Henk, and Jürgen Kirschner — Max Planck Institute of Microstructure Physics, Halle, Germany

Surface alloys of Bi and noble metals on fcc(111) surfaces exhibit Rashba-split occupied sp_z surface states which have been thoroughly investigated by photoemission experiments and electronic-structure calculations. Their unmatched splitting is attributed to the interplay between an in-plane potential gradient and the conventional out-of-plane image-potential gradient. However, the splitting of a set of p_xp_y surface states remained unresolved so far because these unoccupied states cannot be accessed by conventional photoemission.

By angle-resolved two-photon photoemission experiments and first-principles calculations we study in detail the unoccupied p_xp_y states on √3×√3R30^∘-Bi/Cu(111). Their experimental dispersion in the relevant energy range, band maxima (at E_F + 1.4 eV), and momentum offset (0.03 Å⁻¹) agree with the theoretical predictions. Due to their symmetry, these states are expected to be particularly responsive to an in-plane gradient. The abovementioned mechanism and its implications on dispersion and spin polarization are discussed.