Temperature-Resolved Tunneling Spectroscopy Measurements of the Superconducting Energy Gap of Ph-based Iron Pnictides

Multi-gap superconductivity has been observed in various iron-based superconductors. The superconducting energy gaps often depend on the particular manner the crystal has been grown as well as how they are contacted with wire leads. We have performed temperature-resolved tunneling spectroscopy down to 2.0 Kelvin on various dopings of BaFe2(As1-x Px)2. Many of these measurements were performed using soft point contacts with silver paint and some were made using a wire bonder. Features in the differential conductance that can be identified with superconducting energy gaps were tracked with temperature and compared with those we have previously measured using K-doped Ba-122 iron pnictides. All measurements of this work-in-progress were performed fully by undergraduates.