MICROSCOPIC THEORY OF THE DC JOSEPHSON EFFECT IN CLEAN SUPERCONDUCTORINSULATOR AND SUPERCONDUCTOR/SEMICONDUCTOR MULTILAYERS/

We have constructed a fully microscopic self-consistent theory of the de Josephson effect in clean periodic superconducting multilayers with realistic finite-size repulsive barriers, at arbitrary temperatures. We have derived an explicit analytical expression for the critical Jos ephson current j(c) as a function of the superconductor-layer thicknes s a. In the limit a << xi(0). we have found fundamental differences wi th the Ambegaokar-Baratoff relation: a strong reduction of j(c) and an unusual temperature dependence. In this limit, we also predict an exp onential decrease of the critical temperature and the gap parameter du e to the depairing effect of the Josephson current.