Optimizing Sample Preparation for Soft Point Contact Spectroscopy of Iron Pnictude Crystals

Point contact spectroscopy is a widely-used technique for measuring the energy gap of superconductors. Working with iron-based pnictides, particularly K-doped iron pnictide Ba(1-x)KxFe2As2, we have made electrical contact to crystal samples obtained from collaborators by applying a small amount of silver paint using a sharp-tipped wire. We have been moderately successful using this technique and report some results of measurements here. We report progress on ongoing efforts to optimize delivery of silver paint using a more controlled way that employs micro-pipettes. We also present details of how our conductance measurements are influenced by ``fritting'' which is a technique of tuning the point contact region through current impulses. All measurements were performed by undergraduate students.