Near-degeneracy of several pairing channels in multiorbital models for the Fe pnictides

Weak-coupling approaches to the pairing problem in the iron pnictide superconductors have predicted a wide variety of superconducting ground states. We argue here that this is due both to the inadequacy of certain approximations to the effective low-energy band structure, and to the natural near-degeneracy of different pairing channels in superconductors with many distinct Fermi surface sheets. In particular, we review attempts to construct two-orbital effective band models, the argument for their fundamental inconsistency with the symmetry of these materials, and the comparison of the dynamical susceptibilities in two- and five-orbital models. We then present results for the magnetic properties, pairing…

• UD
  U.S. Department of Energy

  Awards: FG02-05ER46236, DE-FG02-, DE-FG02-05ER46236, DE-FG02
• DF
  Deutsche Forschungsgemeinschaft
• OR
  Oak Ridge National Laboratory