d-wave superconductivity of the hole-doped (SrCa)10Cu17O29 ladder compound

Abstract

We performed tunneling experiments on single crystals of hole-doped two-leg ladders (SrCa)10Cu17O29 with Tc≅75 K and, for reference purposes, on textured bulk samples of Bi2Sr2CaCu2O8 (Bi2212). Point-contact and break-junction (Bi2212 only) junction configurations were used. The point-contact junctions, both superconductor–insulator–normal-metal and superconductor–normal-metal, were using Ag counterelectrodes. In all experiments the tunneling direction was along Cu2O3 planes (for the ladders) and CuO2 planes (for Bi2212). The recorded tunneling conductance spectra were reproducible with sharp, well-defined energy-gap structures. All junctions exhibited a pronounced zero-bias conductance peak disappearing at the critical temperature. Experimental results are consistent with the formation of zero-energy Andreev bound states at the surface of the superconductors and dx2−y2-wave symmetry of the order parameter Δ in both compounds.

Source-reported materials — not catalogue approval

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