Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 99: Focus Session: Spins on Surfaces III (joint session O/MA)

O 99.9: Vortrag

Freitag, 5. April 2019, 12:45–13:00, H24

Optical and spin-orbit induced spin orientation of photoelectrons in the soft X-ray range — •Dmitry Vasilyev, Katerina Medjanik, Sergey Babenkov, Martin Ellguth, Gerd Schönhense, and Hans-Joachim Elmers — Institut für Physik, Johannes Gutenberg-Universität, Mainz, Germany

Angular- or k-resolved photoelectron spectroscopy in the soft X-ray range gives access to the bulk electronic structure of materials. Time-of-flight momentum microscopy with parallel spin detection extends this information to the spin degree of freedom. We choose tungsten as a paramagnetic model system in order to exclude any initial-state spin polarization from exchange-split bands. By measurement of four independent photoemission intensities for two opposite spin directions and opposite light helicity, we distinguish between spin polarization contributions of optical spin-orientation by circularly polarized X-rays (Fano component) and a second contribution with polarization direction perpendicular to the scattering plane. The latter phenomenon has been observed for surface states and is usually attributed to the surface-related inversion symmetry breaking. In the case of soft X-ray radiation, only inversion symmetric bulk states of tungsten are probed. Their finite perpendicular spin polarization thus represents a novel phenomenon originating from the spin-dependent interference of final state partial waves.