Electronically-driven lattice distortions in molecule-intercalated iron-chalcogenide superconductors

The electronic nematic phase, which is believed to be a precursor to the superconducting state in high-Tc iron-based superconductors (FeSCs), remains strongly debated. When electronic nematic fluctuations emerge, they reflect on the local environment by imposing subtle lattice modifications not resolved through the average structure. Total scattering studies are sought for a high-Tc (38 K) molecule-intercalated FeSe, where the increased interlayer distance decouples the Fe-selenide sheets, making it an ideal candidate to bring local structural instabilities into light. The experiments will make a model-dependent assessment of the local structure through PDF analysis. The aim is to conclude if the emergence of electronic correlations is responsible for symmetry-lowering transitions at the local level, akin to those accompanying nematic order in FeSCs. The work will shed light on the nature of nematic state and its relationship to the origin of superconducting pairing mechanism.