Quantum point contact conductance in normal metal/insulator/ metal/ mixed wave superconductor junctions

The tunneling conductance in a normal metal/insulator/metal/ d x 2 − y 2 + i d x y mixed wave superconductor (N/I/N/ d x 2 − y 2 + i d x y ) junction is calculated, where the N/I/N region is a quantum wire. It is found in the single-mode case that the magnitude of the tunneling conductance near zero voltage is enhanced due to the Andreev bound state by quasiparticles with perpendicular and horizontal injection, and the zero-bias conductance varies with L ( L is the distance from insulating layer to the interface of N/ d x 2 − y 2 + i d x y mixed wave superconductor). Splitting of the zero-bias conductance peak appears in the quantum point contact tunneling spectra for an N/I/N/ d x 2 − y 2 + i d x y junction, and several subgap peaks can split at the same time. On increasing both L and the magnitude ratio of the two components for the d x 2 − y 2 + i d x y mixed wave, the subgap resonances exhibit an alternately high and low behavior inside the energy gap. These results are different from those in d-wave and p-wave superconductor junctions.