BCS Relation Pressure Dependence of Tin: High-Pressure Point-Contact Spectroscopy Fabrication Improvement

We improved point-contact spectroscopy (PCS) for use under high pressures, wherein the point-contact was directly fabricated on the sample surface using a platinum fine wire and an insulating adhesive lump. We observed point-contact spectra temperature variations on the superconducting state of tin under given pressures. These spectra are well explained by Blonder???Tinkam???Klapwijk theory, which allows us to estimate the superconducting gap from each spectrum. The temperature dependence of the superconducting gap for tin is consistent with the Bardeen???Cooper??? Schrieffer (BCS) curve even under pressures up to 2.26 GPa. The superconducting gap determined at the lowest measured temperature (??0) decreases gradually with increasing pressure, and the ratio between ??0 and Tc remains close to the BCS value with an error of less than 10% as well as under ambient pressure in the whole measured pressure range. The simplified PCS method for use under pressure is easy to use, and the feasibility of high-pressure PCS opens up new possibilities in the study of various materials, such as heavy fermion superconductors.