J61.00007. Unprecedented Optical Anisotropy in Optimally Doped Iron-Based Superconductor

Presented by: Anirban Pal


The divergent nematic susceptibility is empirically found to be a ubiquitous signature in several iron-based materials across their doping-temperature phase diagram, boosting the debate to what extent nematic fluctuations contribute to the pairing-mechanism and generally affect their electronic structure. Here, we offer a comprehensive optical investigation of FeSe as well as of the optimally hole-doped Ba0.6K0.4Fe2As2 over a broad spectral range, as a function of temperature and of tunable applied stress, which acts as an external symmetry breaking field. Our data on FeSe reveal an astonishing optical anisotropy in the infrared-to-visible spectral range, which bears testimony of an important polarization of the underlying electronic structure. The far-infrared response of the charge dynamics moreover allows establishing the link to the dc resistivity, emphasizing scenarios based on scattering by anisotropic spin-fluctuations. At optimal doping the stress-induced optical anisotropy is reversible upon sweeping the applied stress and occurs only below the superconducting transition temperature. These results demonstrate that there is a large electronic nematicity even at optimal doping which extends right under the superconducting dome.


  • Leonardo Degiorgi
  • Anirban Pal
  • Manuel Chinotti


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