Apex oxygen and critical temperature in copper oxide superconductors: Universal correlation with the stability of local singlets
Y. Ohta, T. Tohyama, S. Maekawa
DOI 10.1103/PhysRevB.43.2968 · Physical Review B
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Abstract
Electronic-energy-level structures of the layered Cu oxide compounds are drawn within the ionic model. Correlations between the level separations obtained and the superconducting critical temperature Tc are examined for all families of the Cu oxide superconductors. It is proposed that the position of the energy level of the apex oxygen atoms is of primary importance for the electronic states of the CuO2 plane and governs the optimum Tc’s of all families of hole-carrier suprconductors. The pressure effect of Tc is discussed within this framework. Based on cluster-model calculations, where the covalency neglected in the ionic model is fully taken into account, we argue that the role of the apex oxygen atoms is to prescribe the stability of local singlet states made of two holes in the Cu 3dx2-y2 and O 2pσ orbitals of the CuO2 plane, and thereby to control the maximum Tc of each family.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| La2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 40 | Pressure not reported | onset |
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