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Absence of gross inhomogeneity in HTS cuprates

J. W. Loram, J. L. Tallon, W. Y. Liang

cond-mat.supr-conarXiv:cond-mat/0212461

Abstract

Recent scanning tunnelling microscopy (STM) studies on Bi2Sr2CaCu2O8+δ (Bi-2212) revealed the presence of severe inhomogeneity with length scale L0 ≈ ξ0, the coherence length. Other studies have been interpreted in terms of mesoscale or nanoscale phase segregation. Here we analyze heat capacity and NMR data on Bi-2212 and (Y,Ca)Ba2Cu3O7-δ and find no evidence for phase segregation or gross inhomogeneity. For Bi-2212 the coherence scale L0 increases with doping from 5 to 17ξ0 and the hole density inhomogeneity decreases from 0.028 to 0.005 holes/Cu. We conclude that STM measurements considerably overstate the inhomogeneity in bulk Bi-2212.

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