TUNNELING SPECTRUM INTO A D-WAVE SUPERCONDUCTOR WITH A TIME-REVERSAL-SYMMETRY-BROKEN SURFACE-STATE

Within a Blonder-Tinkham-Klapwijk scattering formalism, the effects of a broken-time-reversal-symmetry (BTRS) surface pairing state on the t ransport properties of a normal-metal-d-wave-superconductor junction h ave been studied by solving the Bogoliubov-de Gennes equations. It has been shown that the zero-bias conductance peak (ZBCP) exhibited in th e pure d-wave case is splitted due to the shift of the midgap state en ergy in the presence of the BTRS state. The splitting of the ZBCP is m ainly determined by the strength of the subdominant s-wave componenet breaking the time-reversal symmetry. If the surface region extends sev eral superconducting coherence lengths, the subgap resonances in condu ctance take place. Very interestingly, the shift of the subgap resonan ce peaks is determined by the relative strength of two components of t he BTRS surface order parameter, regardless of the absolute strength o f them.