Short-Range Nematic Fluctuations in Sr1-xNaxFe2As2 Superconductors

Interactions between nematic fluctuations, magnetic order and superconductivity are central to the physics of iron-based superconductors. Here we report on in-plane transverse acoustic phonons in hole-doped Sr1-xNaxFe2As2 measured via inelastic x-ray scattering, and extract both the nematic susceptibility and the nematic correlation length. By a self-contained method of analysis, for the underdoped (x = 0.36) sample, which harbors a magnetically ordered tetragonal phase, we find it hosts a short nematic correlation length xi similar to 10 angstrom and a large nematic susceptibility chi(nem). The optimal-doped (x = 0.55) sample exhibits weaker phonon softening effects, indicative of both reduced xi and chi(nem). Our results suggest short-range nematic fluctuations may favor superconductivity, placing emphasis on the nematic correlation length for understanding the iron-based superconductors.

Automated summary

In this study, in-plane transverse acoustic phonons in hole-doped Sr1-xNaxFe2As2 were measured via inelastic x-ray scattering, extracting both the nematic susceptibility and nematic correlation length. Short-range nematic fluctuations may favor superconductivity, highlighting the importance of the nematic correlation length in understanding iron-based superconductors.