Experimental phase diagram of moving vortices

TL;DR

This paper maps the phase diagram of moving vortices in a superconducting glass, revealing new phenomena like a peak effect, reentrant depinning, and force-induced pinning, advancing understanding of vortex dynamics under various conditions.

Contribution

The study provides the first comprehensive phase diagram of vortices in a low-pinning superconducting glass as a function of magnetic field, current, and temperature, uncovering novel vortex phases.

Findings

Identification of a large peak effect in vortex behavior

Discovery of a reentrant depinning phase

Observation of a driving force induced pinning phase

Abstract

In the mixed state of type II superconductors, vortices penetrate the sample and form a correlated system due to the screening of supercurrents around them. Interestingly, we can study this correlated system as a function of density and driving force. The density, for instance, is controlled by the magnetic field, B, whereas a current density j acts as a driving force F=jxB on all vortices. The free motion of vortices is inhibited by the presence of an underlying potential, which tends to pin the vortices. Hence, to minimize the pinning strength we studied a superconducting glass in which the depinning current is 10 to 1000 times smaller than in previous studies, which enables us to map out the complete phase diagram in this new regime. The diagram is obtained as a function of B, driving current and temperature and led a remarkable set of new results, which includes a huge peak effect, an additional reentrant depinning phase and a driving force induced pinning phase.