THEORY FOR THE UPPER CRITICAL-FIELD IN SUPERCONDUCTING MULTILAYERS WITH INTERFACE IRREGULARITIES

The upper critical field in superconducting multilayers, which are com posed of two kinds of superconducting layers with different diffusion constants and contain interface irregularities, is investigated in the direction parallel to the layers. The interface irregularities enhanc e the upper critical field. The crossover temperature at which the sup erconducting nucleation position moves from one layer to another is in creased as the effect of the irregularities becomes strong. As a resul t, the two-dimensional region where the nucleation position of the sup erconducting order is inside a layer with the larger diffusion constan t is greatly reduced by the irregularities.