Vortex Glass Scaling of Conductivity

Abstract

The scaling behavior of dc conductivity σ_xx in a current perpendicular to the magnetic field near a vortex-glass (VG) transition is addressed in terms of the Ginzburg-Landau (GL) model and Kubo formula and by assuming a universal scaling behavior of the VG correlation function. Together with the uncorrelated T_c-disorder, we also take account of another type of uncorrelated disorder which becomes a familiar expression once assuming the phase-only approximation. Based on a calculation perturbative in the pinning disorders, we show that both of these uncorrelated disorders are necessary in order to obtain the universal scaling of σ_xx proposed by Fisher et al. [Phys. Rev. B 43 (1991) 130], and that, if either of them is negligible, the scaling behavior of σ_xx can be apparently nonuniversal even deep in the VG critical region. Our results explain, without invoking a possible destruction of true VG transition due to screening, why the vanishing resistivity data show a nonuniversal behavior with a field-dependent exponent in situations with point disorder suppressing the first-order transition.