On voltage-current characteristics and critical current in Bi-2212

Abstract.V(I) characteristics have been performed in a monocrystalline microbridge of Bi[ Pb$]-2212$. The vortex phase diagram has been greatly investigated. Linear but non-ohmic Voltage (Current) (V(I)) curves with a well defined critical current have been observed. A departure from this behavior is observed near the peak effect where an out of equilibrium high threshold current can be stabilized. At high temperature, the critical current persists in the “liquid” state despite the dissipation at the lowest bias. Some implications of these results are discussed. In particular, it is proposed that the surface disorder, rather than the bulk disorder, is responsible for the vortex pinning in this sample.