Orbital angular momentum structure of an unoccupied spin-split quantum-well state in Pb/Cu(111)

Abstract

We performed circular dichroism angle-resolved two-photon photoemission experiments on the quantum-well system one monolayer Pb on Cu(111) to investigate the orbital angular momentum (OAM) structure of the unoccupied quantum-well state. The Pb/Cu(111) system exhibits a small Rashba-type spin-orbit splitting of the unoccupied band around the $\overline{\ensuremath{\Gamma}}$ point and can be referred to as a material system with an intermediate spin-orbit coupling (SOC) parameter. As predicted by Kim et al. [Phys. Rev. B 85, 195402 (2012)], systems with such intermediate SOC strength should show a reversal of the OAM direction for the inner band of a spin-split system. Our results show dichroism values up to $\ifmmode\pm\else\textpm\fi{}20%$ and also the expected change of the dichroism signal at a finite ${k}_{\ensuremath{\parallel}}$ point. The circular dichroism angle-resolved photoemission results therefore support the sensitivity of circular dichroism to OAM texture additionally to spin texture, and also that local OAM must be included to describe the experimentally observed large spin splittings in Rashba systems.