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تسجيل مستخدم جديدNonequilibrium Campbell length: probing the vortex pinning potential
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The $AC$ magnetic penetration depth $lambda (T,H,j)$ was measured in presence of a macroscopic $DC$ (Bean) supercurrent, $j$. In single crystal BSCCO below approximately 28 K, $lambda (T,H,j)$ 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 $j/j_c$. $lambda (T,H,j)$ {it increases} with $j/j_c$ as expected for a non-parabolic potential well whose curvature {it decreases} with the displacement. Qualitatively similar results are observed in other high-$T_{c}$ and conventional superconductors.
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Type-II superconductors owe their magnetic and transport properties to vortex pinning, the immobilization of flux quanta through material inhomogeneities or defects. Characterizing the potential energy landscape for vortices, the pinning landscape (o
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