General features of quantum creep in high- Tc superconductors

Abstract

Measurements of the relaxation rate Q(T) of superconducting currents have been performed on a carefully selected set of dirty and clean high- Tc superconductors for temperatures T down to 100 mK and magnetic fields up to 7 T.The extrapolated relaxation rates Q(0) for the dirty compounds indicate that the viscosity experienced by a tunneling vortex segment is grossly underestimated by the standard Bardeen-Stephen theory.For the clean compounds a universal value Q(0)≅0.022 is found at 1 T, implying that the number of superconducting charge carriers involved in the tunneling of a vortex segment is ≅14. © 1998 The American Physical Society.