NONLINEAR TRANSPORT-PROPERTIES OF SUPERCONDUCTING NANOSTRUCTURES

By solving the Bogoliubov-de Gennes equation seIf-consistently, we com pute transport properties of a one dimensional superconducting island with a delta-function normal scatterer at the centre. The calculated I -V characteristics show significant structure, arising from the compet ition between scattering processes at the boundaries of the island and modification of the order parameter by quasi-particles and superflow. At a certain critical current, the order parameter exhibits a quasi-f irst-order transition to the normal state, smeared by the finite syste m size. At this point, the differential conductance is negative and ca n have a magnitude greater than 2e(2)/h, despite the fact that there i s only a single scattering channel.