Order parameter dimensionality, resistivity and transition temperature in pure and zinc doped YBa_2Cu_3O_(7-y) thin films

摘要

In pure and 0.33% Zn doped (at Cu-site) c-axis oriented laser ablated epitaxial thin films of YBa_2Cu_3O_(7-y) superconductors the excess conductivity, order parameter dimensionality (δ) and the effects of their variation on dimensionality cross-over have been studied. Relative to the dimensionality crossover in pure film the Zn doped film shows fast suppression of superconductivity fluctu-ations. Comparison with other studies indicates: (1) high mean field critical temperature (T_c~(mf)) does not necessarily imply that ρ(T) will be less; (2) for pure films, crossover correlates more with ρ(T) than T_c~(mf); (3) in Zn doped sample order parameter dimensionality δ has an uncertain correlation with ρ(T), but the pure films have an inverse variation; (4) in pure and Zn doped samples δ is directly proportional to T_c~(mf). These suggest inverse correlation between T_c~(mf) and resistivity in the pristine system, which is absent in the case of Zn doped sample.