We address a problem of the upper critical field in a lattice described by a two-dimensional tight-binding model with the on-site pairing. We develop a finite-system approach which enables investigation of magnetic and superconducting properties of electrons on clusters, consisting of a few thousand sites. We present the temperature dependence of the upper critical field and discuss the reentrance of superconductivity for high magnetic field. We also briefly discuss possible extension of the model to account for the properties of high-temperature superconductors.

• Received 22 January 1999

DOI:https://doi.org/10.1103/PhysRevB.60.6300