NORMAL ELECTRON-TUNNELING IN RAMP-TYPE YBCO-JUNCTIONS PREPARED BY LASER-ABLATION

Ramp-type YBa2Cu3O7/insulator/YBa2Cu3O7 junctions have been prepared b y laser ablation. The dependence of the differential conductance on th e voltage is measured at different temperatures and magnetic fields. T he junctions are thermally stable and can be cooled down to liquid hel ium temperature and warmed up again to room temperature several times without quality loss. At temperatures below 35 K they show clear indic ations of an energy gap and in the same temperature range a very sharp zero-bias conductance peak.