Observed regimes of collective flux creep in proton-irradiated, single-crystal Y-Ba-Cu-O: Dependence on current density

Flux-creep studies have quantified the time decay of supercurrents in a proton-irradiated YBa2Cu3O7 crystal. We determine the dependence of the characteristic exponent μ (which governs current decay) on current density and magnetic field. The results are compared with collective-creep theory for the case of random pointlike disorder. Observed are predicted regimes of creep with small and large bundles of vortices, indications of single vortex motion, crossovers in current density, and other qualitative consistencies