Proximity effect in electrodes and the steady-state properties of yosephson SNS structures

Within the framework of microscopic superconductivity theory, influence of the proximity effect in the superconducting electrodes on the critical current (Isub(c)) of long SNS sandwiches is considered. The Isub(c) value is shown to depend essentially on the parameter #betta#=σsub(N)xisub(s)*/σsub(s)xisub(N)* and to be of the same order as I0, the current calculated with no account for suppressed superconductivity in the electrodes, only with #betta# < 0.1. Analytical expressions are derived for cases of high-resistance (#betta# >> 1) and low-resistance (#betta# << 1) N layers, yielding the critical current of a SNS sandwich as a function of the temperature and the parameter #betta#. With arbitrary T and #betta#, the dependences Isub(c)(T, #betta#) are calculated numerically and plotted in graphs which permit to estimate easily to what degree Isub(c) is suppressed owing to the proximity effect