| 1. |
- Dedkov, Y S, et al.
(författare)
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Correlations in the electronic structure of half-metallic ferromagnetic CrO2 films: An x-ray absorption and resonant photoemission spectroscopy study
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 72:6
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of high-quality CrO2(100) films was investigated by means of x-ray absorption and resonant photoemission spectroscopy at the 2p-3d excitation threshold. The obtained binding energy of the occupied Cr 3d states is in agreement with the results predicted within the local spin-density approximation using the dynamical mean-field theory [L. Craco , Phys. Rev. Lett. 90, 237203 (2003)]. The reported data support a model of CrO2 as a half-metallic ferromagnet with strong electron-correlation effects.
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| 2. |
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| 3. |
- Menushenkov, A. P., et al.
(författare)
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Direct evidence of real-space pairing in BaBiO3
- 2024
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Ingår i: Physical Review Research. - : American Physical Society. - 2643-1564. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- The parent compound BaBiO3 of bismuthate high-temperature superconductors (HTSCs) BaBi(Pb)O3 and Ba(K)BiO3 with perovskitelike structure exhibits unusual electronic and structural properties, which can be satisfactorily explained if we assume that all charge carriers are in the paired state. However, the prior experiments and the first-principle calculations only indirectly indicate the existence of paired charge carriers in BaBiO3. In this work, we report the direct evidence of initially paired electrons and holes in the upper antibonding Bi 6s-O 2p sigma* orbital of the neighboring octahedral complexes in the ground state of BaBiO3 using the time-resolved x-ray absorption spectroscopy (XAS) to monitor the electron dynamics after the femtosecond resonant 633 nm laser excitation. We observe strong changes in the oxygen K-edge XAS preedge region, defined by the Bi 6s-O 2p sigma* orbitals. We interpret them as a fast (<= 0.3 ps) breaking of charge carrier pairs and slower (0.3-0.8 ps) lattice rearrangement from the distorted monoclinic structure into the new metastable state with a cubic lattice, which persists at least up to 60 ps after the excitation. Analysis of the intermediate state at the fast excitation shows that the bond disproportionation and monoclinic distortion of BaBiO3 structure are energetically favorable due to the charge carrier pairing. Thus the compound BaBiO3 forms a new quantum state that we define as a local pair density wave. Taking into account a large number of similarities between bismuthate and cuprate high-temperature superconductors, we believe that our work will give a new impetus to understanding the nature of superconductivity in perovskite HTSCs.
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| 4. |
- Grueneis, A., et al.
(författare)
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Electron-electron correlation in graphite : A combined angle-resolved photoemission and first-principles study
- 2008
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:3, s. 037601-
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Tidskriftsartikel (refereegranskat)abstract
- The full three-dimensional dispersion of the pi bands, Fermi velocities, and effective masses are measured with angle-resolved photoemission spectroscopy and compared to first-principles calculations. The band structure by density-functional theory underestimates the slope of the bands and the trigonal warping effect. Including electron-electron correlation on the level of the GW approximation, however, yields remarkable improvement in the vicinity of the Fermi level. This demonstrates the breakdown of the independent electron picture in semimetallic graphite and points toward a pronounced role of electron correlation for the interpretation of transport experiments and double-resonant Raman scattering for a wide range of carbon based materials.
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