Abstract
We use the functional renormalization group to analyze the phase diagram of a four-band model for the iron pnictides subject to band interactions with certain momentum dependence. We determine the parameter regimes where an extended -wave pairing instability with and without nodes emerges. For electron doping, the parameter regime in which a nodal gap appears is in correspondence to recent predictions [A. Chubukov et al., arXiv:0903.5547 (unpublished)], however, at very low . Upon hole doping, the -wave gap never becomes nodal: above a critical strength of the intraband repulsion, the system favors an exotic extended -wave instability on the enlarged hole pockets. At half filling, we find that a strong momentum dependence of interband pair hopping yields an extended -wave instability instead of spin-density wave 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.
- Received 19 October 2009
DOI:https://doi.org/10.1103/PhysRevB.80.180505
©2009 American Physical Society