Rafael M. Fernandes, Andrew J. Millis
Motivated by recent experimental detection of Neel-type ($(\pi,\pi)$) magnetic fluctuations in some iron pnictides, we study the impact of competing $(\pi,\pi)$ and $(\pi,0)$ spin fluctuations on the superconductivity of these materials. We show that even short-range, weak Neel fluctuations strongly suppress the $s^{+-}$ state, with the main effect arising from a repulsive contribution to the $s^{+-}$ pairing interaction, complemented by low frequency inelastic scattering. Further increasing the strength of the Neel fluctuations leads to a low-$T_{c}$ d-wave state, with a possible intermediate $s+id$ phase. The results suggest that the absence of superconductivity in a series of hole-doped pnictides is due to the combination of short-range Neel fluctuations and pair-breaking impurity scattering, and also that $T_{c}$ of the pnictides could be further increased if residual $(\pi,\pi)$ fluctuations could be eliminated.
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http://arxiv.org/abs/1208.3412
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