Critical current density and vortex pinning in tetragonal FeS$_{1-x}$Se$_{x}$ ($x=0,0.06$)

TL;DR

This study investigates the critical current density and vortex pinning mechanisms in tetragonal FeS and Se-doped FeS, revealing enhanced current density with Se doping and identifying dominant vortex pinning interactions.

Contribution

It provides new insights into vortex pinning and critical current enhancement in FeS-based superconductors with Se doping.

Findings

Se doping triples the critical current density.

Vortex pinning is dominated by core-normal surface-like interactions.

Charge carrier scattering with reduced mean free path is the main pinning mechanism.

Abstract

We report critical current density ($J_c$) in tetragonal FeS single crystals, similar to iron based superconductors with much higher superconducting critical temperatures ($T_{c}$'s). The $J_c$ is enhanced 3 times by 6\% Se doping. We observe scaling of the normalized vortex pinning force as a function of reduced field at all temperatures. Vortex pinning in FeS and FeS$_{0.94}$Se$_{0.06}$ shows contribution of core-normal surface-like pinning. Reduced temperature dependence of $J_c$ indicates that dominant interaction of vortex cores and pinning centers is via scattering of charge carriers with reduced mean free path ($\delta$$l$), in contrast to K$_x$Fe$_{2-y}$Se$_2$ where spatial variations in $T_{c}$ ($\delta$$T_{c}$) prevails.