Phase diagrams of singlet superconducting states with mixed symmetry

Abstract

The competition between the singlet superconducting states with s- and d-wave symmetry of the order parameter is studied within a single-band model with nearest-neighbor attractive interaction. The ground state and finite-temperature phase diagrams are constructed for different ratios between the nearest- and next-nearest-neighbor electron transfer integrals. The mixed s+id pairing state is shown to be formed in the intermediate region between s- and d-waves. The temperature phase transitions between the pure and the mixed pairing state are found.