Single-layer oxychloride superconductor Ca2−xCuO2Cl2 with A-site cation deficiency
I. Yamada, A. A. Belik, M. Azuma, S. Harjo, T. Kamiyama, Y. Shimakawa, M. Takano
DOI 10.1103/PhysRevB.72.224503 · Physical Review B
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Abstract
An oxychloride superconductor Ca2−xCuO2Cl2 with a single CuO2 plane in the unit cell was prepared without cation substitution using high-pressure synthesis. The highest TC was 38 K, 10 K higher than that of Ca2−xNaxCuO2Cl2. Structure analysis based on synchrotron x-ray and neutron powder diffractions revealed that the Ca deficiency was the origin of the hole carrier. This compound has two structural features as compared to Ca2−xNaxCuO2Cl2; fewer defects and a shorter Cu-Cl bond length. Postannealing at 773 K led to a further increase of the TC to 43 K. This superconductor with a flat CuO2 plane might form the basis for future discussions about the factors that determine the TC of single-layer cuprates.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Ca2-xCuO2Cl2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 38 | Pressure not reported | onset |
| Ca2-xCuO2Cl2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 43 | Pressure not reported | onset |
| Ca2-xNaxCuO2Cl2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 28 | Pressure not reported | onset |
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