Superconducting order parameter structure in the nematic phase of iron-based materials

TL;DR

This paper investigates how nematic order influences the superconducting pairing symmetry in iron-based superconductors, revealing that nematicity favors an $s_{ ext{pi}\pm}$ state over other pairing types.

Contribution

It models nematic order as a $d$-type Pomeranchuk instability and demonstrates its effect on the superconducting pairing symmetry within a mean-field and spin-fluctuation framework.

Findings

Nematic order with $B_{2g}$ symmetry affects pairing symmetry.

The leading superconducting solution in the nematic phase is $s_{ ext{pi}\pm}$.

Nematicity makes the $s_{ ext{pi}\pm}$ state more favorable than $s_\pm$ or $d_{x^2-y^2}$.

Abstract

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.