Electronic nematic susceptibility of iron-based superconductors

TL;DR

This paper reviews experimental measurements of electronic nematic susceptibility in iron-based superconductors, comparing different methods and discussing its relation to spin and orbital properties, with a focus on FeSe.

Contribution

It provides a comprehensive comparison of nematic susceptibility from shear-modulus, elastoresistivity, and Raman data in Fe-based superconductors, highlighting differences in FeSe.

Findings

Scaling of nematic susceptibility with NMR spin-lattice relaxation rate in BaFe2As2

FeSe shows a large nematic region but no scaling with NMR data

Nematic susceptibility is intricately linked to spin and orbital degrees of freedom.

Abstract

We review our recent experimental results on the electronic nematic phase in electron- and hole-doped BaFe$_2$As$_2$ and FeSe. The nematic susceptibility is extracted from shear-modulus data (obtained using a three-point-bending method in a capacitance dilatometer) using Landau theory and is compared to the nematic susceptibility obtained from elastoresistivity and Raman data. FeSe is particularly interesting in this context, because of a large nematic, i.e., a structurally distorted but paramagnetic, region in its phase diagram. Scaling of the nematic susceptibility with the spin lattice relaxation rate from NMR, as predicted by the spin-nematic theory, is found in both electron- and hole-doped BaFe$_2$As$_2$, but not in FeSe. The intricate relationship of the nematic susceptibility to spin and orbital degrees of freedom is discussed.