Superconducting Order Parameter Structure in the Nematic Phase of Iron-based Materials

We consider the effect of the nematic order on the formation of the superconducting state in iron pnictides and chalcogenides. Nematic order with the $${{B}_{{2g}}}$$ symmetry is modelled as the d-type Pomeranchuk instability and treated within the mean-field approach. Calculated nematic order parameter depends on the nematic interaction coefficient and abruptly changes with the coefficient's increase. The superconducting solution is obtained within the spin-fluctuation pairing theory. We show that the leading solution in the nematic phase has a $${{s}_{{\pi \pm }}}$$ structure. From the critical temperature $${{T}_{c}}$$ estimations, we conclude that the nematic superconducting state of the $${{s}_{{\pi \pm }}}$$ type is more favorable than the usual $${{s}_{ \pm }}$$ and $${{d}_{{{{x}^{2}} - {{y}^{2}}}}}$$ type states appearing in the absence of the nematicity.