Magnetic field tunneling spectroscopy of YBa2Cu3O7-δ/La0.67Sr0.33MnO3 junctions

The magnetic field responses of the zero-bias conductance peaks (ZBCP) in tunneling spectra of YBa2Cu3O7-δ/La0.67Sr0.33MnO3 (YBCO/LSMO) junctions are investigated. Two different responses of the ZBCP are shown. One is insensitive to the field up to 9 T, the other is highly sensitive and easily suppressed by the applied field less than 1 T. Accordingly the origins of the ZBCP are attributed to the mid-gap Andreev bound states and the coherent Andreev reflection, respectively. The coexistence of two different origins in d-wave junction is consistent with the theoretical prediction based on the circuit theory