Formation of Cooper pairs between conduction and localized electrons in heavy-fermion superconductors
arXiv:1205.1869 · doi:10.1103/PhysRevB.87.014516
Abstract
Cooper pairing between a conduction electron ( electron) and an electron, referred to as the "- pairing," is examined to explain s-wave superconductivity in heavy-fermion systems. We first apply the Schrieffer-Wolff transformation to the periodic Anderson model assuming deep level and strong Coulomb repulsion. The resulting effective Hamiltonian contains direct and spin-exchange interactions between and electrons, which are responsible for the formation of the - Cooper pairs. The mean-field analysis shows that the fully gapped - pairing phase with anisotropic s-wave symmetry appears in a large region of the phase diagram. We also find two different types of exotic - pairing phases, the Fulde-Ferrell and breached pairing phases. The formation of the - Cooper pairs is attributed to the fact that the strong Coulomb repulsion makes a quasiparticle band near the center of the conduction band.
7 pages, 6 figures
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