Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides

TL;DR

This study investigates how electron-lattice interactions induce orbital density waves in orthorhombic iron pnictides, revealing their role in stabilizing magnetic order and explaining experimental Fermi surface anisotropies.

Contribution

It demonstrates that electron-lattice coupling leads to orbital density waves that drive magnetic phase transitions in iron pnictides, a novel insight into their electronic behavior.

Findings

F-ODW occurs only in orthorhombic phase

Orbital polarization stabilizes SDW order

Fermi surface anisotropy matches experiments

Abstract

In this paper we explore the magnetic and orbital properties closely related to a tetragonal-orthorhombic structural phase transition in iron pnictides based on both two- and five-orbital Hubbard models. The electron-lattice coupling, which interplays with electronic interaction, is self-consistently treated. Our results reveal that the orbital polarization stabilizes the spin density wave (SDW) order in both tetragonal and orthorhombic phases. However, the ferro-orbital density wave (F-ODW) only occurs in the orthorhombic phase rather than in the tetragonal one. Magnetic moments of Fe are small in the intermediate Coulomb interaction region for the striped antiferromangnetic phase in the realistic five orbital model. The anisotropic Fermi surface in the SDW/ODW orthorhombic phase is well in agreement with the recent angle-resolved photoemission spectroscopy experiments. These results suggest a scenario that the magnetic phase transition is driven by the ODW order mainly arising from the electron-lattice coupling.