We use scanning tunneling microscopy to map the surface structure, nanoscale electronic inhomogeneity, and vitreous vortex phase in the hole-doped superconductor SrKFeAs with K. We find that the low- cleaved surface is dominated by a half Sr/K termination with ordering and ubiquitous superconducting gap, while patches of gapless, unreconstructed As termination appear rarely. The superconducting gap varies by on a 3 nm length scale, with average in the weak-coupling limit. The vortex core size provides a measure of the superconducting coherence length nm. We quantify the vortex lattice correlation length at 9 T in comparison to several iron-based superconductors. The comparison leads us to suggest the importance of dopant size mismatch as a cause of dopant clustering, electronic inhomogeneity, and strong vortex pinning.
- Received 11 December 2012
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