ANALYSIS OF THE FLUCTUATION-INDUCED EXCESS DC CONDUCTIVITY OF EPITAXIAL YBA2CU3O7 FILMS - INFLUENCE OF A SHORT-WAVELENGTH CUTOFF IN THE FLUCTUATION SPECTRUM

Measurements of the temperature dependence of the in-plane dc conductivity on various high-quality epitaxial YBa2Cu3O7 films are presented. The rounding of the resistivity in the transition region has been analyzed in terms of the anisotropic Aslamazov-Larkin (AL), Lawrence-Doniach (LD), and Maki-Thompson theories. In the framework of the time-dependent Ginzburg-Landau (GL) approach we have investigated the influence of a short-wavelength cutoff parameter in the fluctuation spectrum of the AL and LD term. In both theories this physically reasonable cutoff leads to a considerable reduction of the predicted excess de conductivity at higher temperatures. Moreover, the three-dimensional anisotropic AL term, taking the cutoff into account, predicts nearly the same excess conductivity as the original LD term, although these two approaches describe different systems. A good agreement between experimental data and LD as well as the modified three-dimensional anisotropic AL term was found in the region 1.01 T(c) less-than-or-equal-to T less-than-or-equal-to 1.1 T(c). The zero-temperature GL coherence length zeta-c(0) has been estimated to be about 1.5 angstrom.