PHASE-TRANSITIONS WITH THE MIXED-STATE SYMMETRY-BREAKING IN SUPERCONDUCTORS WITH THE ANISOTROPIC PAIRING

In the framework of the Landau approach the symmetry analysis of the phase transition from normal metal to superconductor in magnetic field is developed. All possible irreducible ray representations for this transition are found. The flux line lattice symmetry near H(c2) is discussed. For superconductors with the anisotropic pairing, the situation, when the critical fields of the irreducible representations have the close values is usual. In this case inside the mixed state the phase transition from the single-quantum hexagonal flux-line lattice to the lattice with doubled or tripled number of flux quanta per unit cell or with the reduction of the number of the rotation elements should arise. This theory explains the experimental phase diagram of UPt3.