- https://www.cells.es/ca/actualitat/agenda/esdeveniments-publics-dalba/the-cr-and-cro2-band-structures-revealed-by-bulk-sensitive-soft-x-ray-arpes
- The Cr and CrO2 band structures revealed by bulk sensitive soft-x-ray ARPES
- 2016-01-15T12:00:00+01:00
- 2016-01-15T13:00:00+01:00
- Federico Bisti - Swiss Light Source Paul Scherrer Institute
- Què
- events
- Quan
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Gen 15, 2016
de 12:00 a 13:00 (Europe/Madrid / UTC100) - On
- Sincrotró ALBA - auditori Maxwell
- Nom de contacte
- Massimo Tallarida
- URL de l'esdeveniment
- Lloc web relacionat
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Abstract
The particular photon energies used in the soft x-ray ARPES (300-1000 eV) brings an increase of bulk sensitivity, which implies also the sharpening of the intrinsic accuracy of reciprocal space vector perpendicular to the surface. Moreover, the final-state dispersion becomes free-electron-like which allows accurate determination of the K value distorted during the photoelectron escape into vacuum. These last two points enable precise definition of the full 3D momentum K and thus accurate investigations of electronic structure in 3D materials as in the case of chromium and its dioxide.
Chromium metal presents a complex and interesting magnetic structure featuring, at room temperature, an antiferromagnetic order modulated by a spin-density wave. The data collected on the (100) surface termination has allowed to identify the nesting conditions in the Fermi surface that induces this particular magnetic order. Furthermore the band folding, induced by the magnetic order, has been clearly identified by the comparison with density functional theory calculations. Spurious spectral structures related to final-state effects have been also clarified by the comparison with one-step photoemission calculations.
On the other hand, the large probing depth of soft-X-ray angle resolved photoemission spectroscopy has allowed to establish the electronic band structure of CrO2 through the topmost layer of native amorphous Cr2O3. The experimental data collected so far are able to solve a long debate on the electronic correlation in the system. Indeed, inside the local-spin-density approximation of the density-functional theory, an effective interaction parameter (Ueff=U-J) equal to 1 eV is sufficient for obtaining a good agreement with the data. Furthermore, under the gradient corrections this parameter can be reduced to 0.4 eV. The comparison between the experimental data and the calculation has been possible by unfolding the calculated band structure beyond the translation symmetry limit for simulating the interference effects of the photoemission process.
