EVIDENCE FOR ANOMALOUS FLUCTUATIONS IN SUPERCONDUCTING Bi1.75Pb0.25Ca2Sr2Cu3O10

Abstract
We report very precise measurements of the electrical resistivity of granular Bi 1.75 Pb 0.25- Ca 2 Sr 2 Cu 3 O 10 superconducting ceramics from room temperature down to the superconducting percolating temperature. We analyze the temperature behavior of the excess conductivity and of the temperature derivative variation in electrical resistivity in order to extract the superconductivity fluctuation dimensionality regimes. We obtain unusual power law behaviors which do not correspond to predictions based on Aslamazov and Larkin theory (nor to its generalizations) nor to the regimes found in YBa 2 Cu 3 O 7, e.g., here, dR/dT≃E−11/6 for ln E in [−4,0] with E=|T−T c |T c , where T c is the critical temperature.

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