Observation of a large superconducting gap in Bi-based cuprates by tunneling spectroscopy

Abstract We report that a large superconducting gap has been observed in some tunneling spectra of Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi2212). The observed gap magnitude is roughly twice as large as those of the recent studies of Bi2212. Magnetic susceptibility measurements reveal that the single crystals retain a single phase of Bi2212. Therefore, the experimental results suggest that the large gap arises by way of the superconductor–insulator–superconductor (SIS) tunnel junction, due to the junction interface of the crystal boundary.