Rybkin, A.G.; Shikin, A.M.; Marchenko, D.; Varykhalov, A.; Rader, O.: Spin-dependent avoided-crossing effect on quantum-well states in Al/W(110). Physical Review B 85 (2012), p. 045425/1-7
10.1103/PhysRevB.85.045425

Abstract:
Despite their low atomic number, Al films show large spin-orbit splittings when grown on W(110). Our spin- and angle-resolved photoemission experiment reveals two types of spin-orbit split states: quantum-well states (QWSs) with small Rashba splitting proportional to the electron wave vector in the film plane k [Rashba parameter αR ∼ 7 × 10−12 eVm for a 10-monolayer (ML) film] and substrate-derived interface states with large (∼0.5-eV) splitting. The E(k) dispersion of this pair of interface states changes only slightly up to 3 ML Al. At higher Al coverages, the QWSs and interface states show a remarkable avoided-crossing effect in their band dispersions. This avoided-crossing effect obeys symmetry as well as spin and, therefore, leads to a strongly enhanced spin-orbit splitting of Al QWSs. This is shown by E(k) band dispersions and by spin- and angle-resolved spectra for several thicknesses up to 15 ML Al.