The Gap and the Upper Critical Field as Function of Doping for High- Cuprates

The relation between the -wave superconducting gap and the specific heat obtained with the Volovik effect is used to determine the upper critical field as doping function, for high-temperature superconductors. A two-components model with -wave symmetry, within the BCS framework, is introduced to describe the superconducting state. Generalized Fermi surface topologies are used in order to increase the density of states at the Fermi level, allowing the high- values observed. The electron-phonon interaction is considered the most relevant mechanism for the high- cuprates, where the available phonon energy is provided by the half-breathing modes. The energy gap values calculated with this model are introduced to describe the variation of the upper critical field as function of doping, for .