Direct comparison of Andreev bound states formed at different interfaces using YBa2Cu3O7-y/I/Ag ramp-edge junctions

We present the measurements on, quasiparticle tunneling using YBa2Cu3O7-y/I /Ag ramp-edge junctions to clarify the zero bias conductance peak(ZBCP) rel ated to the Andreev bound states. Two junctions with different tilt angles( 0 degrees and 45 degrees) between the a-axis of YBCO and the junction bound ary are fabricated on the same substrate simultaneously using pulsed laser deposition and Ar ion milling techniques. For the junctions with the tilted angle of 45 degrees ((110) tunneling), a pronounced ZBCP was always observ able, whereas for those fabricated with the tilted angle of 0 degrees, a di p structure at zero bias or a very weak ZBCP was mostly observed. The resul ts are consistent with the recent studies on the Andreev reflection between a d(x)2(-y)2-wave superconductor and a normal metal.