Effects of asymmetric splayed columnar defects on the anomalous peak effect in Ba$_{0.6}$K$_{0.4}$Fe$_{2}$As$_{2}$

TL;DR

This study investigates how asymmetric splayed columnar defects influence the anomalous peak effect in the critical current density of Ba$_{0.6}$K$_{0.4}$Fe$_{2}$As$_{2}$ superconductors, revealing insights into vortex dynamics and defect interactions.

Contribution

It provides new experimental data on the impact of asymmetrically splayed defects on the anomalous peak effect in iron-based superconductors.

Findings

Asymmetric splayed defects affect the APE in $J_c$.

The average direction of splayed CDs influences the APE.

Vortex entanglement relates to the observed APE.

Abstract

In order to enhance the critical current density ($J_c$) of superconductors, introduction of columnar defects (CDs) through swift-particle irradiation is effective. By dispersing the direction of CDs (splayed CDs), not only further enhancement of $J_c$ has been confirmed but also an anomalous peak effect (APE) in $J_c$ at a certain magnetic field determined by the irradiation dose was observed. It has been proposed that the APE arises from the suppression of kink motion and/or the effects of vortex entanglement in systems with splayed CDs. In this study, we measure $J_c$ properties of optimally K-doped Ba-122-type iron-based superconductor Ba$_{0.6}$K$_{0.4}$Fe$_{2}$As$_{2}$ single crystals with splayed CDs that are introduced asymmetrically with respect to the $c$-axis by irradiating 2.6 GeV U ions. We discuss the significance of the average direction of splayed CDs to the APE. We also discuss the relationship between the APE and the entanglement of vortices.