Local inhomogeneity and filamentary superconductivity in Pr-doped CaFe2As2

Phys Rev Lett. 2014 Jan 31;112(4):047005. doi: 10.1103/PhysRevLett.112.047005. Epub 2014 Jan 31.

Abstract

We use multiscale techniques to determine the extent of local inhomogeneity and superconductivity in Ca0.86Pr0.14Fe2As2 single crystal. The inhomogeneity is manifested as a spatial variation of the praseodymium concentration, local density of states, and superconducting order parameter. We show that the high-Tc superconductivity emerges from cloverlike defects associated with Pr dopants. The highest Tc is observed in both the tetragonal and collapsed tetragonal phases, and its filamentary nature is a consequence of nonuniform Pr distribution that develops localized, isolated superconducting regions within the crystals.