L2,3 xanes of the high Tc superconductor YBa2Cu3O≈7 with variable oxygen content

Abstract

Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Bianconi, A., Congiu Castellano, A., Santis, M. D., Rudolf, P., Lagarde, P., Flank, A. M., & Marcelli, A. (1987). L2,3 XANES of the High Tc Superconductor YBa2Cu3O~7 with Variable Oxygen Content. Solid State Communications, 63(11). https://doi.org/10.1016/0038-1098(87)90650-8 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. No evidence of Cu &3d9 final states has been found. This experiment gives direct evidence that additional oxygen x does not give Cu3+ ions with Cu 3d* configuration but gives 3d"L electronic conliguration (I.c. Cu*-Q pairs) and no gap is observed bctwccn the 3d9 (Cu+) and 3d'OL configuration (l.c. C&O-pairs). Thcrcforc in the metallic phase which exhibits superconductivitya continous set of itinerant sta~cs 3d')L and 3ti'"L is obscrvcd. In order to show that the 933 eV peak is quenched with decreasing the oxygen content x we have reduced a sample by heating it in vacuum for 2 h at 400 "C. The 933 eV peak is reduced by the heat treatment as showed in fig. 4 where the spectra of the same sample before and after the heating in vacuum are compared. The difference spectrum between the heated and not heated sample shows a clear maximum at 933 eV and this feature overlaps the high energy side of the white line. THE ELECTRONIC CONFIGURATIONThe spectra of YBa2CU306.5+x (x-0.4) and of the The difference spectrum in fig. 4 shows the lineshape of KCu(biuret)2 show a new feature at 933 eV and 933.7 eV the derivative of the white line which can be assigned to a respectively in comparison with bivalent Cu compounds. In very small energy shift of the white line induced by sample fig. 3 it is clear that in there is an reduction. This shift is in the expected direction but it is overlap between this broad feature at 933 eV and the white smaller than experimental resolution of 0.1 eV.line, while in the insulating KCu(biuret)2 compound they are In order to assign the final state configuration of the 933 completely separated by 3 eV. eV feature we have measured the spectrum of the Cu20

Spatial inhomogeneity and planar symmetry breaking of the lattice incommensurate supermodulation in the high-temperature superconductor Bi2Sr2CaCuPoccia1, Campi2, Fratini3 et al. 2011Phys. Rev. B474580View full textAdd to dashboardCite

“…In cuprates there is agreement on the experimental fact that the itinerant carriers induced by doping are injected in the oxygen 2p orbitals [9] and that at the Fermi level there are two main electronic components [10] x 2 "y 2 orbital. 2) the antinodal particles with lower Fermi velocity with Fermi wavevector in the !…”

“…In fact a variation of 40 % in the amplitude of the structural one-dimensional modulation should make a fuzzy landscape of partial gaps and complex multiple Fermi surfaces. The left-handed distribution of superstructure fluctuation amplitude gives a chiral symmetry at the mcron-scale correlated with the breaking of the rotational symmetry of the rhombic Q 2 distortions of the CuO 4 platelets already observed by EXAFS and resonant diffraction [6][7][8][9][10][11]40]. The misift strain between the superconductor and the spacer layers [18][19][20][21] is proposed to be the external field that breaks the symmetry between the right-handed and the left-handed orientation of the Q 2 distortions [12,13].…”

Soft x-ray absorption and high-resolution powder x-ray diffraction study of superconducting Ca La1−Ba1.75−La0.25+Cu3O system

“…Instead, when oxygen doping increases from heavily underdoped y=6.4 (x=0) to optimum doped y=7.13 (x=0), the feature around 932.9 eV gains its weight, while the feature around 934.3 eV disappears. The shoulder at ~932.9 eV is associated to Cu 3d 9 L → Cu 2p3d 10 L transitions and its spectral weight is proportional to the hole number in the valence band [23,24,[30][31][32][33]. The peak at ~934.3 eV is present only in the spectra of the heavily underdoped samples (y=6.4, x=0 and y=6.4, x=0.3) and is ascribed to Cu 1+ states in the O(4)-Cu(1)-O(4) dumbbell [23][24][25][26].…”

In-Plane Oxygens in High-Temperature Superconducting Cuprates

“…The rapid evolution of the FS with doping in LSCO suggests, assuming the Hartree-Fock (HF) picture, a similar evolution of the Cu vs. O charge content in the SC compositions. On the other hand, notable early XAS [18] and EELS [19] experiment indicates nearly complete oxygen dominance of the conducting bands in both LSCO and YBCO, while the latter shows little FS evolution with doping. Evidently the site content in the conducting states may not be directly inferred from the HF three-band model fits.…”