Peak effect in twinned superconductors

TL;DR

The paper investigates the peak effect in critical current near the melting point of flux lattices in twinned superconductors, attributing it to a transition from collective to strong pinning of vortices on twin boundaries.

Contribution

It proposes a new explanation for the peak effect as a crossover from collective to strong pinning, explaining experimental observations in twinned superconductors.

Findings

Peak effect corresponds to a crossover in pinning regimes.

Sharp transition explains steep resistivity drops.

Applicable to both low and high temperature superconductors.

Abstract

A sharp maximum in the critical current $J_c$ as a function of temperature just below the melting point of the Abrikosov flux lattice has recently been observed in both low and high temperature superconductors. This peak effect is strongest in twinned crystals for fields aligned with the twin planes. We propose that this peak signals the breakdown of the collective pinning regime and the crossover to strong pinning of single vortices on the twin boundaries. This crossover is very sharp and can account for the steep drop of the differential resistivity observed in experiments.