Fermi surfaces of iron-pnictide high-Tc superconductors from the limit   of local magnetic moments
  A 2-orbital t-J model over the square lattice that describes low-energy electronic excitations in iron-pnictide high-Tc superconductors is analyzed with Schwinger-boson-slave-fermion meanfield theory and by exact numerical diagonalization on a finite system. A quantum critical point (QCP) is identified that separates a commensurate spin-density wave (cSDW) state at strong Hund's rule coupling from a hidden half-metal state at weak Hund's rule coupling when inter-orbital hole hopping is suppressed. Low-energy spinwaves that disperse anisotropically from cSDW momenta are predicted at the QCP. Nested Fermi surfaces similar to those observed experimentally in iron-pnictide materials are also predicted in such case. 
J. P. Rodriguez, M. A. N. Araujo, P. D. Sacramento
cond-mat.supr-con cond-mat.str-el