Influence of point defects on the vortex state of disordered superconductors

This is the authors' abstract. We don't add key points for this paper.

We report on a strongly pinned entangled vortex liquid state in the presence of random point disorders in complex ternary (Nd-Eu-Gd)Ba₂Cu₃O_7-δ twinned single-domain melt-textured samples. The in-plane and out-of-plane resistance measurements show that vortex lines are correlated along the c axis with finite vortex correlation length in the pinned liquid state. This is due to the correlated pinning promoted by the twin boundary. The vortex correlation length can be quenched by increasing the defect density by introducing more second-phase precipitates or oxygen defects favoring an entangled vortex liquid state depending on the defect density.