Break-junction tunneling spectra of Bi2212 superconducting ceramics: Influence of inhomogeneous d-wave-Cooper-pairing and charge-density-wave order parameters

摘要

Conductance-voltage characteristics (CVCs) of tunnel break junctions made of Bi2Sr2CaCu2O8+delta crystals were measured. It was demonstrated that the CVCs have a V-shaped inner gap region, similar to those typical of CVCs for tunnel junctions between d-wave superconductors. The CVCs have different forms for different junctions, but all of them reveal weak dip-hump structures outside the inner gap region. Calculations of the tunnel current in the ab plane of the break junctions were carried out in the model of the inhomogeneous d-wave superconductor partially gapped by charge density waves (CDWs). The averaging of the tunnel current over the statistical distributions of both the superconducting and CDW order parameters was carried out. The theoretical results qualitatively reproduce the behavior of experimental curves. A conclusion was made that tunnel directionality and the statistical distributions of both order parameters are crucial factors governing the observed CVC shapes for break junctions made of high-T-c oxides.