Superconducting pairing symmetry and energy gaps of the two-orbital t-t′-J-J′ model: comparisons with the ARPES experiments in iron pnictides

Motivated by the discovery of the iron-based superconductors, we present the theoretical results on the superconducting phase diagram, the temperature-dependent Fermi surface structures in normal state and the angle-resolved photoemission spectroscopy (ARPES) character of quasiparticles of the two-orbital t-t'-J-J' model. In the reasonable physical parameter region of LaFeAsO1-xFx, we find the superconducting phase is stable, and the pairing symmetry is weakly anisotropic and nodeless d(x2-eta y2) + S-x2y2-wave, qualitatively in agreement with the ARPES experiments in iron pnictide superconductors. Nevertheless, the two ratios of the energy gaps to T-c deviate from the ARPES data, suggesting that a more elaborate theoretical model is needed.