Suppression of superconductivity by Neel-type magnetic fluctuations in the iron pnictides

TL;DR

This paper investigates how Neel-type magnetic fluctuations suppress superconductivity in iron pnictides, revealing that even weak fluctuations can significantly reduce $T_c$ and alter pairing symmetry.

Contribution

It demonstrates that short-range Neel fluctuations strongly suppress the $s^{+-}$ superconducting state and can induce a transition to d-wave pairing, providing new insights into magnetic effects on superconductivity.

Findings

Neel fluctuations suppress $s^{+-}$ pairing via repulsive interactions.

Weak Neel fluctuations can induce a transition to d-wave superconductivity.

Absence of superconductivity in some pnictides is due to Neel fluctuations and impurities.

Abstract

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, counter-intuitively, 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 optimally doped pnictides could be further increased if residual $(\pi,\pi)$ fluctuations were reduced.