Observation of a ubiquitous three-dimensional superconducting gap function in optimally-doped Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$

Y. -M. Xu, Y. -B. Huang, X. -Y. Cui +10

The iron-pnictide superconductors have a layered structureformed by stacks of FeAs planes from which the superconductivity originates. Given the multiband and quasi three-dimension…