Orbital-selective superconductivity, gap anisotropy, and spin resonance excitations in a multiorbital t-J 1-model for iron pnictides

We study the orbital-selective superconducting pairing in a five-orbital t-J1-J2 model for iron pnictides. Depending on the orbital selectivity of electron correlations and the orbital characters along the Fermi surface, the superconducting gap in an A1g pairing state may exhibit anisotropy. This anisotropy varies with the degree of J1-J2 magnetic frustration. In the superconducting state, the frequency dependence of the dynamical spin susceptibility at the antiferromagnetic wave vector (π,0) shows a resonance, whose width is enhanced by the orbital selectivity of the superconducting gap. When the degree of the orbital selectivity is sufficiently strong, the resonance peak may be split in two. We discuss the implications of our results on the recent angle-resolved photoemission and neutron-scattering measurements in several superconducting iron pnictides. © 2014 American Physical Society.