Using spin and angle-resolved photoemission spectroscopy we investigate a momentum region in Pb quantum well states on Si(111) where hybridization between Rashba-split bands alters the band structure significantly. Starting from the Rashba regime where the dispersion of the quasi-free two-dimensional electron gas is well described by two spin-polarized parabolas, we find a breakdown of the Rashba behavior which manifests itself (i) in a spin splitting that is no longer proportional to the in-plane momentum and (ii) in a reversal of the sign of the momentum splitting. Our experimental findings are well explained by including interband spin-orbit coupling that mixes Rashba-split states with anti-parallel rather than parallel spins. Similar results for Pb/Cu(111) reveal that the proposed hybridization scenario is independent on the supporting substrate.
@article{arxiv.1306.0245,
title = {Interband spin-orbit coupling between anti-parallel spin states in Pb quantum well states},
author = {Bartosz Slomski and Gabriel Landolt and Stefan Muff and Fabian Meier and Jürg Osterwalder and J. Hugo Dil},
journal= {arXiv preprint arXiv:1306.0245},
year = {2014}
}