Increase of critical current density in FeSe superconductor by strain effect

TL;DR

This study demonstrates that applying compressive strain to FeSe superconductors significantly enhances their critical current density by strengthening vortex pinning, offering a new approach to improve superconductor performance without introducing extrinsic defects.

Contribution

The paper introduces strain engineering as a novel method to enhance the critical current density in FeSe superconductors, shifting pinning mechanisms and improving performance.

Findings

Critical current density increased by a factor of 4 at 2 K under strain.

Order-of-magnitude enhancement of Jc at 5 T due to strain.

Strain shifts vortex pinning from point-like to combined point and surface mechanisms.

Abstract

Conventional $J_c$-enhancement methods like doping and irradiation often introduce extrinsic elements or defects, altering intrinsic properties. Here, we report a significant $J_c$ enhancement in FeSe single crystals through compressive strain applied using a glass-fiber-reinforced plastic substrate with anisotropic thermal contraction during cooling. Under zero field at 2 K, $J_{\text{c}}$ increases by a factor of $\sim$4 from $\sim 2.3 \times 10^{4}$ to $\sim 8.7 \times 10^{4}$ A cm$^{-2}$; at 5 T, it achieves an order-of-magnitude enhancement, rising from $\sim 1.0 \times 10^{3}$ to $\sim 1.0 \times 10^{4}$ A cm$^{-2}$. Analysis based on the Dew-Hughes model of the $f_{\text{p}}$(h) relationship shows that strain strengthens vortex pinning, and shifts the pinning mechanism from point-like pinning to combined point and surface pinnings. This work offers an effective method to enhance FeSe's current-carrying limitation, deepens understanding of iron-based superconductors' pinning mechanisms, and highlights strain engineering's potential for optimizing superconducting performance.