Peak Effect in Superconductors: Absence of Phase Transition and Possibility of Jamming in Vortex Matter

TL;DR

This study numerically investigates the peak effect in disordered superconductors, showing it results from vortex jamming rather than a phase transition, with continuous structural changes observed across the peak.

Contribution

It demonstrates that the peak effect arises from vortex jamming without an associated phase transition, challenging previous theories of an order-disorder transition.

Findings

Critical current increases near Bc2, exhibiting peak effect behavior.

Vortex configurations change continuously from ordered to amorphous states.

No evidence of a phase transition near the peak effect.

Abstract

The magnetic field $B$ dependence of the critical current $I_c$ for the vortex phase of a disordered superconductor is studied numerically at zero temperature. The $I_{c}(B)$ increases rapidly near the upper critical field $B_{c2}$ similar to the peak effect (PE) phenomenon observed in many superconductors. The real space configuration across the PE changes continuously from a partially ordered domain (polycrystalline) state into an amorphous state. The topological defect density $n_{d}(B)\sim e^{\alpha B^{k}}$ with $k>1$ for $B\geq 0.4B_{c2}$. There is no evidence of a phase transition in the vicinity of the PE suggesting that an order-disorder transition is not essential for the occurrence of the PE phenomenon. An alternative view is presented wherein the vortex system with high dislocation density undergoes jamming at the onset of the PE.