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A common characteristic of many “overdoped” cuprates prepared with high-pressure oxygen is Tc values ≥ 50 K that often exceed that of optimally doped parent compounds, despite O stoichiometries that place the materials at the edge or outside of the conventional boundary between superconducting and normal Fermi liquid states. X-ray absorption fine-structure (XAFS) measurements at 52 K on samples of high-pressure oxygen (HPO) YSr2Cu2.75Mo0.25O7.54, Tc = 84 K show that the Mo is in the (VI) valence in an unusually undistorted octahedral geometry with predominantly Mo neighbors that is consistent with its assigned substitution for Cu in the chain sites of the structure. Perturbations of the Cu environments are minimal, although the Cu X-ray absorption near-edge structure (XANES) differs from that in other cuprates. The primary deviation from the crystal structure is therefore nanophase separation into …
National Academy of Sciences
Publication date: 
3 Mar 2020

Steven D Conradson, Theodore H Geballe, Andrea Gauzzi, Maarit Karppinen, Changqing Jin, Gianguido Baldinozzi, Wenmin Li, Lipeng Cao, Edmondo Gilioli, Jack M Jiang, Matthew Latimer, Oliver Mueller, Venera Nasretdinova

Biblio References: 
Volume: 117 Issue: 9 Pages: 4559-4564
Proceedings of the National Academy of Sciences