| 1. |
- Sanchez-Barriga, J., et al.
(författare)
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Effects of spin-dependent quasiparticle renormalization in Fe, Co, and Ni photoemission spectra : An experimental and theoretical study
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 85:20, s. 205109-
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the spin-dependent quasiparticle lifetimes and the strength of electron correlation effects in the ferromagnetic 3d transition metals Fe, Co, and Ni by means of spin- and angle-resolved photoemission spectroscopy. The experimental data are accompanied by state-of-the-art many-body calculations within the dynamical mean-field theory and the three-body scattering approximation, including fully relativistic calculations of the photoemission process within the one-step model. Our quantitative analysis reveals that inclusion of local many-body Coulomb interactions are of ultimate importance for a realistic description of correlation effects in ferromagnetic 3d transition metals. However, we found that more sophisticated many-body calculations with larger modifications in the case of Fe and Co are still needed to improve the quantitative agreement between experiment and theory. In general, it turned out that not only the dispersion behavior of energetic structures should be affected by nonlocal correlations but also the line widths of most of the photoemission peaks are underestimated by the current theoretical approaches. The increasing values of the on-site Coulomb interaction parameter U and the band narrowing of majority spin states obtained when moving from Fe to Ni indicate that the effect of nonlocal correlations becomes weaker with increasing atomic number, whereas correlation effects tend to be stronger.
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| 2. |
- Sanchez-Barriga, J., et al.
(författare)
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Quantitative determination of spin-dependent quasiparticle lifetimes and electronic correlations in hcp cobalt
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:10, s. 104414-
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Tidskriftsartikel (refereegranskat)abstract
- We report on a quantitative investigation of the spin-dependent quasiparticle lifetimes and electron correlation effects in ferromagnetic hcp Co (0001) by means of spin-and angle-resolved photoemission spectroscopies. The experimental spectra are compared in detail to state-of-the-art many-body calculations within the dynamical mean-field theory and the three-body scattering approximation, including a full calculation of the one-step photoemission process. From this comparison we conclude that although strong local many-body Coulomb interactions are of major importance for the qualitative description of correlation effects in Co, more sophisticated many-body calculations are needed in order to improve the quantitative agreement between theory and experiment, in particular, concerning the linewidths. The quality of the overall agreement obtained for Co indicates that the effect of nonlocal correlations becomes weaker with increasing atomic number.
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| 3. |
- Sanchez-Barriga, J., et al.
(författare)
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Strength of Correlation Effects in the Electronic Structure of Iron
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:26, s. 267203-
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Tidskriftsartikel (refereegranskat)abstract
- The strength of electronic correlation effects in the spin-dependent electronic structure of ferromagnetic bcc Fe(110) has been investigated by means of spin and angle-resolved photoemission spectroscopy. The experimental results are compared to theoretical calculations within the three-body scattering approximation and within the dynamical mean-field theory, together with one-step model calculations of the photoemission process. This comparison indicates that the present state of the art many-body calculations, although improving the description of correlation effects in Fe, give too small mass renormalizations and scattering rates thus demanding more refined many-body theories including nonlocal fluctuations.
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| 4. |
- Krivenkov, M., et al.
(författare)
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Lifshitz transition in titanium carbide driven by a graphene overlayer
- 2023
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Ingår i: Physical Review Research. - 2643-1564. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) Dirac materials are electronically and structurally very sensitive to proximity effects. We demonstrate, however, the opposite effect: that the deposition of a monolayer 2D material could exercise a substantial influence on the substrate electronic structure. Here we investigate TiC(111) and show that a graphene overlayer produces a proximity effect, changing the Fermi surface topology of the TiC from six electron pockets to one hole pocket on the depth of several atomic layers inside the substrate. In addition, the graphene electronic structure undergoes an extreme modification as well. While the Dirac cone remains gapless, it experiences an energy shift of 1.0 eV beyond what was recently achieved for the Lifshitz transition of overdoped graphene. Due to this shift, the antibonding π∗ band at the M¯ point becomes occupied and observable by photoemission.
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| 5. |
- Mertins, H-Ch., et al.
(författare)
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Magneto-optical reflection spectroscopy on graphene/Co in the soft x-ray range
- 2017
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 903
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Tidskriftsartikel (refereegranskat)abstract
- The existence of ferromagnetic ordering in graphene on cobalt is demonstrated by means of resonant magnetic reflection spectroscopy exploiting the transversal magneto-optical Kerr-effect (T-MOKE). Using linearly polarized synchrotron radiation in the soft x-ray range with energies spanning the carbon 1s edge, the π- and σ- bonds of graphene were excited individually, showing that magnetism in graphene is carried by the π – orbitals. Magnetic signals were detected over a wide energy range from 257 – 340 eV with a T-MOKE peak value of 1.1 % at the π – resonance energy near 285 eV. By comparison with corresponding spectra measured at the 2p edges of the Co substrate, a large induced magnetic moment of 0.14 μB was derived for graphene. Individual hysteresis curves monitored at the Co 2p and C 1s edges show that the carbon magnetism is induced by the Co substrate.
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| 6. |
- Usachov, D. Yu, et al.
(författare)
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Cubic Rashba Effect in the Surface Spin Structure of Rare-Earth Ternary Materials
- 2020
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Ingår i: Physical Review Letters. - 0031-9007. ; 124:23
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Tidskriftsartikel (refereegranskat)abstract
- Spin-orbit interaction and structure inversion asymmetry in combination with magnetic ordering is a promising route to novel materials with highly mobile spin-polarized carriers at the surface. Spin-resolved measurements of the photoemission current from the Si-terminated surface of the antiferromagnet TbRh2Si2 and their analysis within an ab initio one-step theory unveil an unusual triple winding of the electron spin along the fourfold-symmetric constant energy contours of the surface states. A two-band k·p model is presented that yields the triple winding as a cubic Rashba effect. The curious in-plane spin-momentum locking is remarkably robust and remains intact across a paramagnetic-antiferromagnetic transition in spite of spin-orbit interaction on Rh atoms being considerably weaker than the out-of-plane exchange field due to the Tb 4f moments.
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