The upper critical field for coupled layered superconductors with local pairs is analyzed within the mean-field approach for the anisotropic negative-U Hubbard model. Effects of reduced dimensionality are investigated by solving the Ginzburg-Landau equations to obtain critical fields for different anisotropy ratios. The Harper’s-type system of equations is solved analytically for some special field values. Limitations of Peierls substitution are also discussed.

• Received 2 September 1993

DOI:https://doi.org/10.1103/PhysRevB.49.6372