Positron trapping at defects in copper oxide superconductors

T. McMullen; P. Jena; S. N. Khanna; Yi Li; Kjeld O. Jensen

doi:10.1103/PhysRevB.43.10422

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Positron trapping at defects in copper oxide superconductors

T. McMullen, P. Jena, S. N. Khanna, Yi Li, Kjeld O. Jensen

DOI 10.1103/PhysRevB.43.10422 · Physical Review B

T1

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Abstract

Positron states and lifetimes at defects in the copper oxide superconductors La2−xSrxCuO4, YBa2Cu3O7−x, and Bi2Sr2CaCu2O8+x are calculated with use of the superposed-atom model. In the Bi2Sr2CaCu2O8+x compound, we find that the smaller metal-ion vacancies appear to only bind positrons weakly, while missing oxygens do not trap positrons. In contrast, metal-ion vacancies in La2−xSrxCuO4 and YBa2Cu3O7−x bind positrons by ∼1 eV, and oxygen-related defects appear to be the weak-binding sites in these materials. The sites that bind positrons only weakly, by energies ∼kBT, are of particular interest in view of the complex temperature dependences of the annihilation characteristics that are observed in these materials.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
La2-xSrxCuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O7-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Bi2Sr2CaCu2O8+x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O6.8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O7.0 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
La1.85Sr0.15CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown