Low energy gap-like structure in YBa/sub 2/Cu/sub 3/O/sub 7-x//metal junctions

Low-energy gap-like structures were experimentally observed in different types of tunnel junctions with base electrodes of high-temperature superconductor (HTS) and upper electrodes of low-temperature superconductor (LTS) or normal metal. The resulting structures are interpreted as arising from a sum of LTS and HTS gaps resulting from the strong depression of superconductivity in HTS near the tunneling barrier due to the outdiffusion of oxygen. This conclusion is confirmed by the temperature and magnetic field dependence of the structures. The energy gap of a degraded HTS layer was found to be about 1.6 meV, with ratio 2 Delta /sub L//k/sub B/T/sub c/=4.1 and critical temperature T/sub c/ equivalent to 9 K.<
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