Coherence Length of Electronic Nematicity in Iron-Based Superconductors

Recent developments in laser-excited photoemission electron microscopy (laser-PEEM) advance the visualization of electronic nematicity and nematic domain structures in iron-based superconductors. In FeSe and BaFe\(_2\)(As\(_{0.87}\)P\(_{0.13}\))\(_2\) superconductors, it has been reported that the thickness of the electronic nematic domain walls is unexpectedly long, leading to the formation of mesoscopic nematicity wave [T. Shimojima \(\textit{et al.}\), Science \(\textbf{373}\) (2021) 1122]. This finding demonstrates that the nematic coherence length \(\xi_{\rm nem}\) can be decoupled from the lattice domain wall. Here, we report that the electronic domain wall thickness shows a distinct variation in related materials: it is similarly long in FeSe\(_{0.9}\)S\(_{0.1}\) whereas it is much shorter in undoped BaFe\(_2\)As\(_2\). We find a correlation between the thick domain walls and the non-Fermi liquid properties of normal-state resistivity above the nematic transition temperature. This suggests that the nematic coherence length can be enhanced by underlying spin-orbital fluctuations responsible for the anomalous transport properties.