Magneto-orbital coupling in iron pnictides

A magneto-orbital coupling mechanism is proposed to account for the weak energy gap at the Fermi energy in the (π,0) ordered SDW state of a realistic three-orbital model for iron pnictides involving dxz, dyz, and dxy Fe orbitals. The orbital mixing terms between the dxy and dxz/dyz orbitals, which are important in reproducing the orbital composition of the elliptical electron pockets at (±π,0) and (0,±π), are shown to play a key role in the energy gap formation in the SDW state.