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Anomalous expansion of the copper-apical-oxygen distance in superconducting cuprate bilayers

By Hua Zhou, Yizhak Yacoby, Vladimir Y. Butko, Gennady Logvenov, Ivan Božović and Ron Pindak


We have introduced an improved x-ray phase-retrieval method with unprecedented speed of convergence and precision, and used it to determine with sub-Ångstrom resolution the complete atomic structure of epitaxial La2-xSrxCuO4 ultrathin films. We focus on superconducting heterostructures built from constituent materials that are not superconducting in bulk samples. Single-phase metallic or superconducting films are also studied for comparison. The results show that this phase-retrieval diffraction method enables accurate measurement of structural modifications in near-surface layers, which may be critically important for elucidation of surface-sensitive experiments. Specifically we find that, while the copper-apical-oxygen distance remains approximately constant in single-phase films, it shows a dramatic increase from the metallic-insulating interface of the bilayer towards the surface by as much as 0.45 Å. The apical-oxygen displacement is known to have a profound effect on the superconducting transition temperature

Topics: Physical Sciences
Publisher: National Academy of Sciences
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Provided by: PubMed Central
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