Anisotropy of the coherence length from critical currents in the stoichiometric superconductor LiFeAs

TL;DR

This study measures the directional critical currents in LiFeAs to determine the anisotropy of the coherence length, revealing that it decreases with increasing magnetic field, thus providing insights into vortex behavior in this superconductor.

Contribution

The paper introduces a method to extract the coherence length anisotropy parameter in LiFeAs from critical current measurements in the low-field regime.

Findings

Critical current anisotropy is determined by coherence length anisotropy.

Increasing magnetic field reduces the coherence length anisotropy.

Measurements are performed far below the upper critical field B_c2.

Abstract

Miniature Hall-probe arrays were used to measure the critical current densities for the three main directions of vortex motion in the stoichiometric LiFeAs superconductor. These correspond to vortices oriented along the c-axis moving parallel to the ab-plane, and to vortices in the ab-plane moving perpendicular to, and within the plane, respectively. The measurements were carried out in the low-field regime of strong vortex pinning, in which the critical current anisotropy is solely determined by the coherence length anisotropy parameter, {\epsilon}_{\xi}. This allows extraction of {\epsilon}_{\xi} at magnetic fields far below the upper critical field B_c2. We find that increasing magnetic field decreases the anisotropy of the coherence length.