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arXiv · 2601.02707

Energy-Resolved Real-Space Imaging of Orbital Nematicity in an Fe-Based Superconductor

Asato Onishi·Zifan Xu·Cédric Bareille·Yoichi Kageyama·Shigeyuki Ishida·Hiroshi Eisaki·Kota Ishihara·Kenichiro Hashimoto·Toshiyuki Taniuchi·Takasada Shibauchi
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Abstract

Electronic nematicity in Fe-based superconductors is manifested by spontaneous rotational symmetry breaking and the formation of nematic domains with mutually orthogonal directions of $d_{xz}$/$d_{yz}$ orbital anisotropy. However, its energy dependence has remained largely unexplored in real space. Using 5.82-eV laser-excited photoemission electron microscopy (laser-PEEM) with an energy-selective slit, we visualize the evolution of linear dichroic (LD) contrast within individual nematic domains of Ba$_{1-x}$Na$_x$Fe$_2$As$_2$ ($x\approx0.08$). We discover a sign reversal of the LD contrast at an energy $\sim0.4$ eV below the Fermi level, directly revealing an inversion of orbital anisotropy inside each domain. This behavior reflects a different energy-dependent redistribution of spectral weight between the $d_{xz}$ and $d_{yz}$ states, highlighting the crucial role of orbital-selective coherence in the nematic phase of Fe-based superconductors.

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Asato Onishi, Zifan Xu, Cédric Bareille, Yoichi Kageyama, Shigeyuki Ishida, Hiroshi Eisaki, Kota Ishihara, Kenichiro Hashimoto, Toshiyuki Taniuchi, Takasada Shibauchi. 2026-01-06. Energy-Resolved Real-Space Imaging of Orbital Nematicity in an Fe-Based Superconductor. https://doi.org/10.7566/jpsj.95.033701

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