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.