Results of Point-Contact Spectroscopy Measurements of the Energy Gap of Ph-doped Iron Pnictides BaFe 2 (As 1-x P x ) 2*

The study of multi-band superconductivity has gained momentum over the past few years, especially
with the advent of iron-based superconductors where multiple energy gaps have been observed. The
observed energy gaps which are anisotropic largely depend on the way that the crystal has been grown
and how contact is made to access tunneling directions. Soft point contacts to the crystals studied were
carefully made using silver paint. We report the results of four-wire tunneling spectroscopy
measurements of the energy gap of phosphorus-doped iron pnictides BaFe 2 (As 1-x P x ) 2 where x = 0.204,
0.304, 0.25, 0.39, 0.43 and 0.69. The differential conductance dI/dV of these samples exhibit broad
peaks and shoulders with Δ 1 = 2-5 meV, and Δ 2 = 7-10 meV. Some of these results were reproducible
over similar samples, correspond well with existing data from literature while other features appear new.
We report temperature-dependent features that we are in the process of anayzing. These measurements
were performed fully by undergraduates.