Magnetism and Superconductivity in the Two-Dimensional 16-Band d–p Model for Iron-Based Superconductors

Abstract

The electronic states of the Fe₂As₂ plane in iron-based superconductors are investigated on the basis of the two-dimensional 16-band d–p model which includes the Coulomb interaction on a Fe site: the intra- and inter-orbital direct terms U and U′, the Hund’s coupling J and the pair-transfer J′. Using the random phase approximation (RPA), we obtain the magnetic phase diagram including the stripe and the incommensurate order on the U′–J plane. We also solve the superconducting gap equation within the RPA and find that, for large J, the most favorable pairing symmetry is extended s-wave whose order parameter changes its sign between the hole pockets and the electron pockets, while it is d_xy-wave for small J.