Quasiparticle bound states and low-temperature peaks of the conductance of NIS junctions in d-wave superconductors
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Contributions of quasiparticle states, bound to the boundary of anisotropically paired superconductors, to the density of states and to the conductance of normal-metal-insulator-superconduction (NIS) junctions are studied both analytically and numerically. For smooth surfaces and real order parameters, we find some general results for the bound-state energies. In particular, we show that under fairly general conditions quasiparticle states with nonzero energies exist for momentum directions within a narrow region around the surface normal. The energy dispersion of the bound states always has an extremum for the direction along the normal. Along with the zero-bias anomaly due to midgap states, we find, for quasi-two-dimensional materials, additional low-temperature peaks in the conductance of NIS junctions for voltages determined by the extrema of the bound-state energies. The influence of interface roughness on the conductance is investigated within the framework of Ovchinnikovs model. We show that nonzero-bias peaks at low temperatures may give information on the order parameter in the bulk, even though it is suppressed at the surface. 1997 The American Physical Society.
author list (cited authors)
Barash, Y. S., Svidzinsky, A. A., & Burkhardt, H.
complete list of authors
Barash, YS||Svidzinsky, AA||Burkhardt, H