4D texture of circular dichroism in soft-x-ray photoemission from tungsten

Photoemission-intensity distributions IRCP/LCP (EB, k) measured for right- and left-circularly polarized soft x-rays revealed a large circular dichroism in angular distribution (CDAD) in the 4D parameter space (EB binding energy, k momentum vector). Full-field k-imaging combined with time-of-flight...

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Bibliographic Details
Published in:New journal of physics 2019-01, Vol.21 (1), p.13017
Main Authors: Fedchenko, O, Medjanik, K, Chernov, S, Kutnyakhov, D, Ellguth, M, Oelsner, A, Schönhense, B, Peixoto, T R F, Lutz, P, Min, C-H, Reinert, F, Däster, S, Acremann, Y, Viefhaus, J, Wurth, W, Braun, J, Minár, J, Ebert, H, Elmers, H J, Schönhense, G
Format: Article
Language:English
Subjects:
Adsorbates
Angular distribution
Binding energy
Brillouin zones
circular dichroism
Circular polarization
Dichroism
Mapping
Momentum
Photoelectric emission
photoemission
Photons
Physics
Planes
Polarimeters
Soft x rays
Symmetry
ToF momentum microscopy
Tungsten
X-rays
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Summary:Photoemission-intensity distributions IRCP/LCP (EB, k) measured for right- and left-circularly polarized soft x-rays revealed a large circular dichroism in angular distribution (CDAD) in the 4D parameter space (EB binding energy, k momentum vector). Full-field k-imaging combined with time-of-flight energy recording at a high-brilliance soft x-ray beamline allowed mapping the CDAD in the bulk Brillouin zone of tungsten and the entire d-band complex within a few hours. CDAD-asymmetries are very high (up to 90%), persist throughout the whole photon-energy range (300-1300 eV) and show a pronounced dependence on momentum k and binding energy EB, visualized as movies or sequences of cuts through the 4D object. One-step photoemission calculations for the same photon energies show fair agreement with the measured results. In addition to the requirement of a 'handed' experimental geometry, known from previous experiments on adsorbates and surface states, we find an anti-symmetric behavior of the CDAD with respect to two bulk mirror planes. A new symmetry condition along the perpendicular momentum kz makes CDAD a valuable tool for an unambiguous identification of high-symmetry planes in direct transitions in the periodic zone scheme. Technically, the method provides a circular polarimeter for soft, tender and hard x-rays.
ISSN:1367-2630
1367-2630
DOI:10.1088/1367-2630/aaf4cd