Strong 3D correlations in vortex system of Bi2212:Pb

TL;DR

This study investigates magnetic flux penetration in Bi2212:Pb superconductors, revealing a temperature-dependent transition at 54K that signifies a shift from 3D vortex correlations to decoupled pancake vortices, explaining strong pinning effects.

Contribution

It provides experimental evidence of a temperature-induced transition from 3D vortex correlations to decoupled vortices in Bi2212:Pb, enhancing understanding of vortex behavior and pinning mechanisms.

Findings

Flux anisotropy increases with temperature up to 54K.

At 54K, flux behavior abruptly changes, losing correlation.

Transition temperature is independent of magnetic field strength.

Abstract

The experimental study of magnetic flux penetration under crossed magnetic fields in Bi2212:Pb single crystal performed by magnetooptic technique (MO) reveals remarkable field penetration pattern alteration (flux configuration change) and superconducting current anisotropy enhancement by the in-plane field. The anisotropy increases with the temperature rise up to $T_m = 54 \pm 2 K$. At $T = T_m$ an abrupt change in the flux behavior is found; the correlation between the in-plane magnetic field and the out-of-plane magnetic flux penetration disappears. No correlation is observed for $T > T_m$. The transition temperature $T_m$ does not depend on the magnetic field strength. The observed flux penetration anisotropy is considered as an evidence of a strong 3D - correlation between pancake vortices in different CuO planes at $T < T_m$. This enables understanding of a remarkable pinning observed in Bi2212:Pb at low temperatures.