THEORY OF THE UPPER CRITICAL FIELD OF SUPERCONDUCTING SUPERLATTICES.

The upper critical field of superconducting superlattices is calculated by taking account of spatial variations of the density of states and the diffusion constant of conduction electrons, and the attractive interaction constant responsible for superconductivity. The spatial variation of the density of states is most important for explaining the dimensional crossover from three-dimensional behavior to two-dimensional behavior in the temperature dependence of the upper critical field observed by Schuller et al.