Difference in anisotropic vortex pinning in pristine and proton-irradiated (Ca0.85La0.15)10(Pt3As8)(Fe2As2)5 single crystals

Abstract

To study the difference in the vortex pinning mechanism between in-plane and out-of-plane and the change of these pinning mechanisms due to defects induced by proton irradiation, the in-plane electrical resistivity for pristine and proton irradiated (Ca0.85La0.15)10(Pt3As8)(Fe2As2)5 single crystals in B//c and B//ab up to B = 13 T. Both samples showed a monoclinic crystal structure, which was different from previously known, through crystal structure analysis using the selected area electron diffraction (SAED) method. The protons irradiation incident along the c-axis caused expansion of the lattice constants a and b. The electronic structure changed by the expansion of this lattice constant affected the change of the coherence length ξc significantly shorter than the distance between the superconducting Fe2As2 layers. The vortex in B//ab was mainly pinned by the newly formed normal component with zero Cooper pair due to the short ξc, and ξc increased by proton irradiation reduced the pinning energy. On the other hand, the vortex in B//c was mainly pinned by point defects, and the point defects increased by proton irradiation increased the pinning energy.