Orbital-weight redistribution triggered by spin order in the pnictides...

The one-particle spectral function and its orbital composition are investigated in a three-orbital model for the
undoped parent compounds of the iron-based superconductors. In the realistic parameter regime, where results
fit experimental data best, it is observed that the magnetization in the xz and yz orbitals are markedly different
and the Fermi surface presents mostly xz character, as recently observed in photoemission experiments
T. Shimojima et al., Phys. Rev. Lett. 104, 057002
2010. Since the ferro-orbital order in this regime is at
most a few percent, these results are mainly driven by the magnetic order. An analogous analysis for a
five-orbital model leads to similar conclusions.