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.