  Influence of surface pair breaking, barrier transmission and phase difference
on quasiparticle bound states in junctions with d-wave superconductors is
examined. Based on the quasiclassical theory of superconductivity, an approach
is developed to handle interface bound states. It is shown in SIS' junctions
that low energy bound states get their energies reduced by surface pair
breaking, which can be taken into account by introducing an effective order
parameter for each superconductor at the junction barrier. More interestingly,
for the interface bound states near the continuous spectrum the effect of
surface pair breaking may result in a splitting of the bound states. In the
tunneling limit this can lead to a square root dependence of a nonequilibrium
Josephson current on the barrier transmision, which means an enhancement as
compared to the conventional critical current linear in the transmission.
Reduced broadening of bound states in NIS junctions due to surface pair
breaking is found.
