Non-Linear Effects During Vortex Motion in Superconducting Films of Nd _1.85 Ce _0.15 CuO _<i>x</i>

Abstract

As predicted by Larkin and Ovchinnikov, in the low-temperature limit the flux-flow resistance of a type-II superconductor displays a logarithmic singularity at an electric current I* which originates from the contraction of the vortex core first discussed by Kramer and Pesch and which is related to the critical pair-breaking current and the inelastic quasi-particle scattering rate τin-1. We report the first observation of this effect, performing our experiments with epitaxial c-axis-oriented films of Nd1.85Ce0.15CuOx. Near 1.6 K for the inelastic-scattering rate we obtained a value as low as τin-1 = 1.7 · 109 s-1.