We discuss general implications of the local spin-triplet pairing among correlated fermions that is induced by the Hunds rule coupling in orbitally degenerate systems. The quasiparticle energies, the magnetic moment, and the superconducting gap are determined for principal superconducting phases, in the situation with the exchange field induced by both the local Coulomb and the Hunds rule exchange interactions. The phase diagram, as well as the evolution in an applied magnetic field of the spin-triplet paired states near the Stoner threshold is provided for a model two-band system. The appearance of the spin-polarized superconducting phase makes the Stoner threshold a hidden critical point, since the pairing creates a small but detectable uniform magnetization. The stability of the superconducting state against the ferromagnetism with an alternant orbital ordering appearing in the strong-coupling limit is also discussed.
تحميل البحث