Abstract
We investigate the electronic reconstruction across the tetragonal-orthorhombic structural transition in FeSe by employing polarization-dependent angle-resolved photoemission spectroscopy on detwinned single crystals. Across the structural transition, the electronic structures around the and points are modified from fourfold to twofold symmetry due to the lifting of degeneracy in orbitals. The band shifts upward at the point, while it moves downward at the point, suggesting that the electronic structure of orthorhombic FeSe is characterized by a momentum-dependent sign-changing orbital polarization. Due to this sign-changing orbital order, the elongated directions of the elliptical Fermi surfaces at the and points are rotated by 90° with respect to each other, which makes the nesting condition between these FSs imperfect. The present result, supported by calculations, indicates the possible suppression of the spin-fluctuation mediated superconductivity in the orthorhombic FeSe, as compared to the orbital-ordered state without sign change.
- Received 3 April 2015
- Revised 17 October 2015
DOI:https://doi.org/10.1103/PhysRevB.92.205117
©2015 American Physical Society