Upper critical fields and order parameters of layered superconductors in a continuous Ginzburg-Landau model

In this paper, we report our extensive investigations of layered superconductors within a continuous Ginzburg-Landau model. The calculated results suggest that the parallel upper critical field generally increases with the transition temperature and may be correlated with the behaviours of the order parameters. The calculated upper critical fields of MgB2 are in reasonably good agreement with experiment. The obtained order parameters of MgB2, YBCO and Hg1223 respectively demonstrate a three-dimensional, quasi-three-dimensional and two-dimensional behaviour, as expected. (author)