Dimensionality of the Superconductivity in YBa2Cu3O7-δ

Superconducting fluctuation-induced diamagnetism was observed in YBa 2 Cu 3 O 7-δ with different oxygen deficiencies. In a slightly deficient sample, the fluctuation is small and exhibits the temperature dependence of a three-dimensional nature. With increasing defects, however, the fluctuations were found to be enhanced and exhibit a crossover from three- to two-dimensional behaviors at higher temperatures. The dimensionality, which is controlled by the interlayer coupling between the CuO 2 planes, is very sensitive to oxygen deficiency in the CuO chains, even when the critical temperature remains around 90 K.