title: Multi-orbital quantum antiferromagnetism in iron pnictides-effective spin couplings and quantum corrections to sublattice magnetization.
abstract: Effective spin couplings and spin fluctuation induced quantum corrections to sublattice magnetization are obtained in the [Formula: see text] AF state of a realistic three-orbital interacting electron model involving xz, yz and xy Fe 3d orbitals, providing insight into the multi-orbital quantum antiferromagnetism in iron pnictides. The xy orbital is found to be mainly responsible for the generation of strong ferromagnetic spin coupling in the b direction, which is critically important to fully account for the spin wave dispersion as measured in inelastic neutron scattering experiments. The ferromagnetic spin coupling is strongly suppressed as the xy band approaches half filling, and is ascribed to particle-hole exchange in the partially filled xy band. The strongest AF spin coupling in the a direction is found to be in the orbital off-diagonal sector involving the xz and xy orbitals. First order quantum corrections to sublattice magnetization are evaluated for the three orbitals, and yield a significant [Formula: see text] average reduction from the Hartree-Fock value.
authors.affiliation: Department of Physics, Indian Institute of Technology Kanpur 208016, India.
authors.forename: Sayandip
authors.initials: S
authors.lastname: Ghosh
authors.forename: Nimisha
authors.initials: N
authors.lastname: Raghuvanshi
authors.forename: Shubhajyoti
authors.initials: S
authors.lastname: Mohapatra
authors.forename: Ashish
authors.initials: A
authors.lastname: Kumar
authors.forename: Avinash
authors.initials: A
authors.lastname: Singh