Point Contact Spectroscopy of Iron Pnictides: Probing Superconductors to Observe the Gap Structures of (P, Co, K) Doped Iron Pnictides*

We used a four-wire point contact spectroscopy system to obtain differential conductance (dI/dV) measurements in order to observe the energy gap structures of phosphorus, cobalt, and potasium doped iron-pnictides with varying doping levels at 2K. We were motivated to study the iron pnictides because they were only recently discovered to be superconducting (~2007) due to the presence of iron which is traditionally expected to quench all superconducting properties, and also because the iron pnictides can exhibit multi-gap structures like those of magnesium di-boride. Our goal was to obtain the differential conductance measurements for varying x values of phosphorus,cobalt, and potassium, and observe the gap structures of the various families to further characterize and understand the superconducting transition of these iron pnictides. We observed both single and double gap structures for various x values, with delta 1 ~ 2-5 meV, and delta 2 ~ 7-10 meV. We will report additional results from this ongoing work.