title: Spin-orbit interactions and the nematicity observed in the fe-based superconductors.
abstract: High-resolution angle-resolved photoelectron spectroscopy is used to examine the electronic band structure of FeTe_{0.5}Se_{0.5} near the Brillouin zone center. A consistent separation of the α_{1} and α_{2} bands is observed with little k_{z} dependence of the α_{1} band. First-principles calculations for bulk and thin films demonstrate that the antiferromagnetic coupling between the Fe atoms and hybridization-induced spin-orbit effects lifts the degeneracy of the Fe d_{xz} and d_{yz} orbitals at the zone center leading to orbital ordering. These experimental and computational results provide a natural microscopic basis for the nematicity observed in the Fe-based superconductors.
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Johnson
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: H-B
authors.initials: HB
authors.lastname: Yang
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Rameau
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Gu
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Z-H
authors.initials: ZH
authors.lastname: Pan
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: T
authors.initials: T
authors.lastname: Valla
authors.affiliation: Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA.
authors.forename: M
authors.initials: M
authors.lastname: Weinert
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Fedorov