Nematicity as a probe of superconducting pairing in iron-based superconductors

TL;DR

This paper investigates how nematic order influences superconducting pairing in iron-based superconductors, revealing that nematicity can enhance transition temperatures and alter pairing symmetry, serving as a diagnostic for unconventional pairing states.

Contribution

It demonstrates the strong coupling between nematicity and superconductivity, showing how nematic fluctuations can modify pairing symmetry and transition characteristics in iron-based superconductors.

Findings

Nematic order causes a sharp increase in $T_c$.

Nematic fluctuations can favor an intermediate pairing state.

Strong softening of shear modulus observed across $T_c$.

Abstract

In several families of iron-based superconducting materials, a d-wave pairing instability may compete with the leading s-wave instability. Here we show that when both states have comparable free energies, superconducting and nematic degrees of freedom are strongly coupled. While nematic order causes a sharp non-analytic increase in $T_{c}$, nematic fluctuations can change the character of the s-wave to d-wave transition, favoring an intermediate state that does not break time-reversal symmetry but does break tetragonal symmetry. The coupling between superconductivity and nematicity is also manifested in the strong softening of the shear modulus across the superconducting transition. Our results show that nematicity can be used as a diagnostic tool to search for unconventional pairing states in iron pnictides and chalcogenides.