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

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.

5 pages, 4 figures