Localized holes in superconducting lanthanum cuprate

P. C. Hammel; B. W. Statt; R. L. Martin; F. C. Chou; D. C. Johnston; S-W. Cheong

doi:10.1103/PhysRevB.57.R712

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Localized holes in superconducting lanthanum cuprate

P. C. Hammel, B. W. Statt, R. L. Martin, F. C. Chou, D. C. Johnston, S-W. Cheong

DOI 10.1103/PhysRevB.57.R712 · Physical Review B

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Abstract

Copper NQR spectra demonstrate the existence of a second, anomalous copper site in lanthanum cuprate whose character is independent of the method of doping. We present a systematic NMR/NQR study of La2CuO4+δ for a range of δ, which demonstrates that the density of such sites increases with δ. Analysis of our results and of published data from La2−xSrxCuO4 indicate that a substantial fraction of the doped holes in these materials localize in CuO6 octahedra adjacent to the out-of-plane dopants, and that the anomalous sites are those neighboring a site occupied by such a pinned hole. Thus, superconductivity occurs in a CuO2 plane containing many localized holes.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
La2CuO4+δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	40	Pressure not reported	onset
La2CuO4.12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	58	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