1997/01/29 by J. Röhler, Röhler, J., P. W. Loeffen +7
Physics and Astronomy · #FOS: Physical sciences #Magnetic properties of thin films #Physics of Superconductivity and Magnetism #Scientific Research and Discoveries #Superconductivity (cond-mat.supr-con) #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/9701208
33 pages, 20 figures (GIF format). Kluwer macro included. To be published in the NATO ASI Series. "Materials Aspects of High-T_c Superconductivity: 10 Years After the Discovery" (Kluwer, Dordrecht)
arxiv created 1997/01/29 · openalex publication_date 1997/01/29 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/02
We have measured the extended x-ray absorption-fine-structure (EXAFS) at the Y-K edge of YBa2Cu3Ox for x=6.801, 6.947, 6.968, 6.984 at T=20-300 K. Across the underdoped-overdoped transition the Y-Cu2 pairs exhibit harmonic vibrations which freeze out in the superconducting phase, whereas the Y-O2,3 pairs exhibit strong anharmonicities with a singularity at Tc. In the underdoped regime the average spacing O2,3-Cu2 increases with x due to displacements of Cu2 towards Ba, but the average position of O2,3 along c is almost unaffected. Optimum doping is a notable point in the x-T phase diagram, also concerning the lattice degrees of freedom. Here the O2,3-Cu2 spacing (buckling) is largest, and in the superconducting phase the Cu2 position along the c-axis is independent on temperature. In the overdoped regime increasing x displaces the Cu2 along c further towards Ba, but the O2,3 layer starts to shift in the same direction, thus decreasing the O2,3-Cu2 spacing.