Investigation of superconducting gap structure in TbFeAsO0.9F0.1 using point contact Andreev reflection

Bulk samples of TbFeAsO0.9F0.1 (T-c(on) = 50 K) were measured by point contact Andreev reflection spectroscopy. The spectra show unambiguous evidence for multiple gap-like features plus the presence of high-bias shoulders. By measuring the spectra as a function of temperature with both gold and superconducting niobium tips, we establish that the gap-like features are associated with the superconducting order parameter in this material. We discuss whether the well-defined zero-bias conductance peak that we observe infrequently is associated with a nodal superconducting order parameter.