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 ${\alpha }_1$ and ${\alpha }_2$ bands is observed with little $k_z$ dependence of the ${\alpha }_1$ 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.

11 pages, 4 figures, 20 references