Reproducible tunneling data on chemically etched single crystals of YBa2Cu3O7

Tunnel junctions have been fabricated between chemically etched single crystals of YBa2Cu3O7 and evaporated metal counterelectrodes and found to exhibit reproducible characteristics. Above the bulk Tc of YBa2Cu3O7, the conductance G(V) has a linear dependence with voltage and has some asymmetry. Below Tc, additional structure associated with the superconductivity appears in G(V). At T much less than Tc there is a reproducible finite zero-bias conductance, which suggests that there are states at the Fermi energy in superconducting YBa2Cu3O7. Junctions with Pb, Sn, Bi, Sb, PbBi, and Au counterelectrodes all show qualitatively similar behavior. (Author)