Tunneling spectroscopy of the superconducting gap in (formula presented)

The tunneling technique with a break junction has been applied to investigate the multiple superconducting gaps in (formula presented) The observed gap features can be explained by combining inherent and induced order parameters. The largest gap of (formula presented) corresponds to a very strong-coupling ratio (formula presented) Upon warming, this gap decreases in accordance with the BCS dependence, while the smaller gaps reduce faster than that but persist up to (formula presented) Therefore, the smallest gap of (formula presented) gives (formula presented) The magnetic field can distinguish the behavior of the gap. The extrapolated highest gap-closing field for the largest gap agrees with the upper-critical field, thereby indicating that this gap is predominant to (formula presented).