Monday, July 1, 2013

1306.6727 (Sayandip Ghosh et al.)

Orbital order induced stabilization of the (π,0) ordered magnetic
state in a minimal two-band model for iron pnictides

Sayandip Ghosh, Avinash Singh
Spin wave excitations and stability of the (\pi,0) ordered magnetic state are investigated in a minimal two-band itinerant-electron model for iron pnictides. Presence of hopping anisotropy generates a strong ferro-orbital order in the d_{xz} and d_{yz} Fe orbitals. The orbital order sign is as observed in experiments. By optimizing the strength of the emergent AF and F spin couplings through optimal band fillings in the two orbitals, the induced ferro-orbital order is shown to strongly enhance the spin wave energy scale and stabilize the magnetic state. The calculated spin-wave dispersion is in quantitative agreement with neutron scattering measurements. Finite inter-orbital Hund's coupling is shown to strongly stabilize the SDW state by coupling the two magnetic sub-systems.
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