Self-doping processes between planes and chains in the metal-to-superconductor transition of YBa2Cu3O6.9.
The interplay between the quasi 1-dimensional CuO-chains and the 2-dimensional CuO2 planes of YBa(2)Cu(3)O(6+x) (YBCO) has been in focus for a long time. Although the CuO-chains are known to be important as charge reservoirs that enable superconductivity for a range of oxygen doping levels in YBCO, the understanding of the dynamics of its temperature-driven metal-superconductor transition (MST) remains a challenge. We present a combined study using x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) revealing how a reconstruction of the apical O(4)-derived interplanar orbitals during the MST of optimally doped YBCO leads to substantial hole-transfer from the chains into the planes, i.e. self-doping. Our ionic model calculations show that localized divalent charge-transfer configurations are expected to be abundant in the chains of YBCO. While these indeed appear in the RIXS spectra from YBCO in the normal, metallic, state, they are largely suppressed in the superconducting state and, instead, signatures of Cu trivalent charge-transfer configurations in the planes become enhanced. In the quest for understanding the fundamental mechanism for high-Tc-superconductivity (HTSC) in perovskite cuprate materials, the observation of such an interplanar self-doping process in YBCO opens a unique novel channel for studying the dynamics of HTSC.
Department of Physics, Chemistry and Biology, IFM, Thin Film Physics Division, Linköping University, SE-58183 Linköping, Sweden.
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Magnuson
Paul Scherrer Institut, Swiss Light Source (SLS), CH-5232 Villigen PSI, Switzerland.
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Schmitt
Paul Scherrer Institut, Swiss Light Source (SLS), CH-5232 Villigen PSI, Switzerland.
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Strocov
1] Paul Scherrer Institut, Swiss Light Source (SLS), CH-5232 Villigen PSI, Switzerland [2] Institut Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung (G-ISRR), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, D-12489 Berlin, Germany.
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Schlappa
Quantum Devices Physics Group, Department of Microtechnology and Nanoscience-MC2, Chalmers University of Technology, SE412 96 Gothenburg, Sweden.
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Kalabukhov
Department of Physics and Astronomy, Division of Molecular and Condensed Matter Physics, Uppsala University, Box 516, S-751 20 Uppsala, Sweden.
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Duda