Multi-orbital quantum antiferromagnetism in iron pnictides --- effective spin couplings and quantum corrections to sublattice magnetization

TL;DR

This paper investigates the multi-orbital quantum antiferromagnetism in iron pnictides, focusing on effective spin couplings and quantum corrections to magnetization, revealing orbital-specific interactions and significant quantum effects.

Contribution

It provides a detailed analysis of spin couplings and quantum corrections in a realistic three-band model of iron pnictides, highlighting the role of the $xy$ orbital and orbital off-diagonal interactions.

Findings

The $xy$ orbital causes strong ferromagnetic coupling in the $b$ direction.

Ferromagnetic coupling diminishes near half filling of the $xy$ band.

Quantum corrections reduce sublattice magnetization by 37%.

Abstract

Towards understanding the multi-orbital quantum antiferromagnetism in iron pnictides, effective spin couplings and spin fluctuation induced quantum corrections to sublattice magnetization are obtained in the $(\pi,0)$ AF state of a realistic three band interacting electron model involving $xz$, $yz$, and $xy$ Fe 3d orbitals. 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 $37\%$ average reduction from the Hartree-Fock value.