Point contact spectroscopy of Co-doped pnictide superconductors*

Iron pnictides are an interesting material for superconductivity research, since they provide a contrasting system for high temperature superconductivity to the cuprates. Point-contact spectroscopy is a unique method which has been used for investigating the density of states of cuprate superconductors and can help shed light on the pnictide superconductors as well. Point-contact measurements have an advantage over tunneling spectroscopy since they are less sensitive to sample surface quality and the dimensionless barrier parameter Z, can be varied with contact pressure. We have performed point contact measurements using an apparatus with a capacitive displacement sensor which enables us to systematically vary Z. We will present point contact spectra obtained on single crystal Ba(Fe$_{0.926}$Co$_{0.074)2}$As$_{2}$ samples and other cobalt doped iron pnictide samples at various temperatures, magnetic fields, and Z.