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

TL;DR

This paper investigates the voltage-current behavior and critical current in a Bi-2212 superconductor, revealing non-ohmic characteristics, the influence of surface disorder on vortex pinning, and the persistence of critical current in the vortex liquid state.

Contribution

It provides new insights into vortex dynamics and pinning mechanisms in Bi-2212, emphasizing the role of surface disorder over bulk disorder.

Findings

Linear but non-ohmic V(I) curves with well-defined critical current

High threshold current near the peak effect

Critical current persists in the vortex liquid state at high temperature

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 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.