Unconventional superconductivity and interaction induced Fermi surface   reconstruction in the two-dimensional Edwards model
  We study the competition between unconventional superconducting pairing and charge density wave (CDW) formation for the two-dimensional Edwards Hamiltonian at half filling, a very general two-dimensional transport model in which fermionic charge carriers couple to a correlated background medium. Using the projective renormalization method we find that a strong renormalization of the original fermionic band causes a new hole-like Fermi surface to emerge near the center of the Brillouin zone, before it eventually gives rise to the formation of a charge density wave. On the new, disconnected parts of the Fermi surface superconductivity is induced with a sign-changing order parameter. We discuss these findings in the light of recent experiments on iron-based oxypnictide superconductors. 
Dai-Ning Cho, Jeroen van den Brink, Holger Fehske, Klaus W. Becker,   Steffen Sykora
cond-mat.str-el