ab Plane Point Contact Spectroscopy of Co-doped Iron Pnictide Superconductors

Point contact measurements on iron-based superconductors provide valuable information about these new superconductors, including gap sizes, number of gaps, and gap symmetries. We use a point contact apparatus capable of taking measurements in the ab{\-}plane using a tungsten wire lowered mechanically onto a superconducting sample. Using this method allows us to measure the variation of superconducting gap(s) with Z, a dimensionless barrier strength parameter. Previous point contact measurements have shown Co-doped iron pnictide superconductors to be a two gapped material. Our measurements confirm the presence of two gaps in single crystal Ba(Fe$_{0.926}$Co$_{0.074)2}$As$_{2}$ and the Z variation of the measurements imply the gaps are isotropic. Acknowledgments: NSF DMR-0804452, DOE contract {\#} DE-FG02-86ER45268