Momentum-dependent sign-inversion of orbital polarization in superconducting FeSe

TL;DR

This study reveals a momentum-dependent sign-inversion of orbital polarization in FeSe across its structural transition, showing how electronic structures evolve and suggesting a link to its unique magnetic properties.

Contribution

It uncovers a momentum-dependent sign change in orbital polarization in FeSe, advancing understanding of its electronic reconstruction during the structural transition.

Findings

Orbital polarization sign changes between G and M points.

Electronic structure shifts indicate momentum-dependent orbital behavior.

Fermi surface elongation directions rotate by 90 degrees.

Abstract

We investigate the electronic reconstruction across the tetragonal-orthorhombic structural transition in FeSe by employing polarization-dependent angle-resolved photoemission spectroscopy (ARPES) on detwinned single crystals. Across the structural transition, the electronic structures around the G and M points are modified from four-fold to two-fold symmetry due to the lifting of degeneracy in dxz/dyz orbitals. The dxz band shifts upward at the G point while it moves downward at the M point, suggesting that the electronic structure of orthorhombic FeSe is characterized by a momentum-dependent sign-changing orbital polarization. The elongated directions of the elliptical Fermi surfaces (FSs) at the G and M points are rotated by 90 degrees with respect to each other, which may be related to the absence of the antiferromagnetic order in FeSe.