Giant increase in critical current density of KxFe2-ySe2 single crystals

TL;DR

This study demonstrates a significant enhancement in the critical current density of KxFe2-ySe2 single crystals through post-annealing and quenching, revealing insights into vortex pinning mechanisms and potential for improved superconductor performance.

Contribution

The paper introduces a post-annealing and quenching method that substantially increases the critical current density in KxFe2-ySe2 crystals and analyzes the dominant vortex pinning mechanisms involved.

Findings

Critical current density increased by over tenfold to ~2.1 x 10^4 A/cm^2 at 1.8 K.

Presence of a single dominant pinning mechanism across all measured temperatures.

Identification of 3D point-like normal core pinning sources and delta Tc pinning in quenched samples.

Abstract

By using post-annealing and quenching technique, we show that the critical current density Jc,ab of KxFe2-ySe2 single crystals can be enhanced more than one order of magnitude up to ~ 2.1 \times 10^4 A/cm^2 at 1.8 K. The scaling law between normalized pinning force and reduced field for all measured temperatures was observed, reflecting the presence of only one dominant pinning mechanism. Analysis indicates presence of 3D point-like normal core pinning sources in quenched KxFe2-ySe2 samples whereas dominant vortex interaction with pinning centers is via spatial variations in Tc ("deltaTc pinning").