Normal electron tunnelling in ramp-type YBCO-junctions prepared by laser ablation

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