FLUCTUATIONS OF THE CRITICAL-CURRENT THROUGH JOSEPHSON-JUNCTIONS WITH DIRTY NORMAL-METAL BARRIERS

Josephson currents in superconductor-normal metal-superconductor junctions are studied numerically when the normal metal region is in the diffusive regime. The average critical current and the fluctuations of the critical current are calculated as a function of the length of the normal metal region L. In the case where L is shorter than the coherence length of the superconductor xi, the magnitude of the fluctuations is shown to be of order eDELTA/hBAR (DELTA is the pair potential). When L is several times as long as xi, numerical results suggest that the fluctuations become of order e square-root DELTAE(c)/hBAR (E(c) is the correlation energy). These results are compared with previous theoretical studies.