Huge metastability in high-Tc superconductors induced by parallel magnetic field -: art. no. 092511

We present a study of the temperature-magnetic-field phase diagram of homogeneous and inhomogeneous superconductivity in the case of a quasi-two-dimensional superconductor with an extended saddle point in the energy dispersion under a parallel magnetic field. At low temperature, a huge metastability region appears, limited above by a steep superheating critical field H-sh and below by a strongly reentrant supercooling field H-sc. We show that the Pauli limit H-p for the upper critical magnetic field is strongly enhanced due to the presence of the Van Hove singularity in the density of states. The formation of a nonuniform superconducting state is predicted to be very unlikely.