Properties of HTS step-edge SNS junctions
The critical current and current-voltage characteristics of step-edge HTS SNS junctions are discussed theoretically. In accordance with the experimental data it is assumed that the current transport through both NS interfaces takes place in ab-direction. In the bottom interface ((001) surface of YBCO) the ab-coupling may occur due to atomic steps which play a role of constrictions for the current flow. Therefore the contact is modelled as SNS structure with system of constrictions located at both interfaces. The IcRN product and the excess current Iex are calculated as a function of temperature, interface transparency and N layer thickness. It is shown that in accordance with the experimental data the Iex and Ic are of the same order of magnitude in a broad parameter range.