THE CONSTRICTION MODEL FOR SNS JOSEPHSON-JUNCTIONS

The approach developed by Blender, Tinkham and Klapwijk (BTK) for calc ulation of the quasiparticle (qp) current in NcS contacts is generaliz ed to the case of ScNS and SNcNS contacts with disordered NS electrode s. Amplitudes of Andreev and normal reflections at the ballistic const riction are calculated. The relation between the qp current and energy spectrum of NS proximity sandwich is found for arbitrary transparenci es of the constriction and NS interfaces. The appearance of new series of subharmonic peaks associated with the two-gap structure in the den sity of states of NS electrodes is demonstrated. The model is also app lied to calculation of the critical and the excess currents in ScNS an d SNcNS for different interface parameters. The relevance of the model to transport mechanisms in step-edge NTS SNS contacts is discussed.