Nonequilibrium Campbell length: probing the vortex pinning potential

Original · EN

The AC magnetic penetration depth λ(T,H,j) was measured in presence of a macroscopic DC (Bean) supercurrent, j. In single crystal BSCCO below approximately 28 K, λ(T,H,j) exhibits thermal hysteresis. The irreversibility arises from a shift of the vortex position within its pinning well as j changes. It is demonstrated that below a new irreversibility temperature, the nonequilibrium Campbell length depends upon the ratio j/jc. λ(T,H,j) increases with j/jc as expected for a non-parabolic potential well whose curvature decreases with the displacement. Qualitatively similar results are observed in other high-Tc and conventional superconductors.