Quasi-particle interference and possible orbital order in FeSe
ORAL
Abstract
Spontaneous formation of unidirectional electronic states or nematicity in iron-based superconductors has attracted much attention but spectroscopic understanding of nematicity is still elusive. Using scanning tunneling microscopy/spectroscopy, we have investigated FeSe which becomes superconducting in an orthorhombic phase. Spectroscopic imaging over wide energy range ($\pm$50 meV) revealed clear quasi-particle interference (QPI) patterns. In the Fourier-transformed spectroscopic images, we identified unidirectional electron- and hole-like QPI branches, which disperse in orthogonal directions. We argue this behavior in connection to the orbital ordering in the orthorhombic phase.
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