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

作者：Zhou Hua; Yacoby Yizhak; Butko Vladimir Y; Logvenov Gennady; Bozovic Ivan; Pindak Ron^*

来源：Proceedings of the National Academy of Sciences of the United States of America, 2010, 107(18): 8103-8107.

DOI：10.1073/pnas.0914702107

• complex oxide
• epitaxial film
• interface superconductivity
• phase-retrieval
• surface diffraction

We have introduced an improved x-ray phase-retrieval method with unprecedented speed of convergence and precision, and used it to determine with sub-Angstrom 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 angstrom. The apical-oxygen displacement is known to have a profound effect on the superconducting transition temperature.

• 出版日期2010-5-4