Thermally activated depinning of a driven flux line lattice

We have performed simultaneous measurements of the resonance frequency, dam ping and resistivity of vibrating Y123 thin films to study the behavior of the depinning of a driven flux line lattice (FLL). The measurements show: ( i) the depinning temperature remains unaffected up to a current density of 10(6) A/m(2); (ii) at higher currents the depinning temperature and the wid th of the dissipation peak as a function of temperature decrease whereas it s height increases; (iii) at high enough currents the dissipation at the de pinning saturates. The observed "motional narrowing" appears to be in agree ment with recently published ideas on a driven FLL with disorder recovering a quasiordered or "Bragg-glass" state by sliding it at high enough velocit ies. The dissipation peak measured at high currents can be quantitatively u nderstood with a diffusion model without free parameters.