Nematic correlation length iron-based superconductors probed by inelastic x-ray scattering [in press]

Nematicity is ubiquitous in electronic phases of high-Tc superconductors, particularly in the Fe-based systems. We used inelastic x-ray scattering to extract the temperature-dependent nematic correlation length ξ from the anomalous softening of acoustic phonon modes in FeSe, underdoped Ba(Fe0.97Co0.03)2As2 and optimally doped Ba(Fe0.94Co0.06)2As2. In all cases, we find that ξ is well described by a power law (T−T0)−1/2 extending over a wide temperature range. We attributed this mean-field behavior and the extended fluctuation regime to a sizable nemato-elastic coupling, which may be detrimental to superconductivity.