SUPERCONDUCTING CURRENT IN A BALLISTIC DOUBLE SUPERCONDUCTING NORMAL-METAL SUPERCONDUCTING STRUCTURE

Using the Bogoliubov-de Gennes equation, we study superconducting current in a ballistic double superconducting-normal-metal-superconducting (SNSNS) structure. There are two contributions to the current: current I1 due to the discrete part of the excitation spectrum and current I2 due to the continuous part of the spectrum. Bound states (Andreev levels) are associated to each normal region. If the length L of the middle S region is comparable to (or smaller than) the coherence length ξ0, the Andreev levels in different regions interact; if Lξ0 the Andreev levels are noninteracting. The interaction between the Andreev levels influences I1. Moreover, I2 is negligible only in the limits Lξ0 and Lξ0. We present curves for the dependence of the critical current Ic on L and on the pair potential of the middle S region. The pair potential of the middle S region prevents reduction of Ic. The effects we study will not be present in a transfer Hamiltonian approach. © 1995 The American Physical Society.