2009/06/24 by Ronny Thomale, Christian Platt, Jiangping Hu +2
Physics and Astronomy · #cond-mat.supr-con
published as Phys. Rev. B 80, 180505(R) (2009). · 6 pages, 6 figures
arxiv created 2009/06/24 · arxiv updated 2009/12/01
We use the functional renormalization group method to analyze the phase diagram of a 4-band model for the iron-pnictides subject to band interactions with certain A1g momentum dependence. We determine the parameter regimes where an extended s-wave pairing instability with and without nodes emerges. On the electron-doped side, the parameter regime in which a nodal gap appears is found to be much narrower than recently predicted in arXiv:0903.5547. On the hole-doped side, the extended s-wave pairing never becomes nodal: above a critical strength of the intra-band repulsion, the system favors an exotic extended d-wave instability on the enlarged hole pockets at much lower Tc. At half filling, we find that a strong momentum dependence of inter-band pair hopping yields an extended s-wave instability instead of spin-density wave (SDW) ordering. These results demonstrate that an interaction anisotropy around the Fermi surfaces generally leads to a pronounced sensitivity of the pairing state on the system parameters.