Changes of the Fermi Surface Topology in the Three-orbital Model for Iron Pnictides with the Spin-orbit Coupling

Ivanov, D.A., Togushova, Y.N., Korshunov, M.M.// Journal of Siberian Federal University - Mathematics and Physics//

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Effect of the spin-orbit coupling on the band structure and the Fermi surface of the three-orbital model is studied. The inter-orbital part of the model is reformulated to fully conform with the iron lattice symmetry. Because there are two iron ions in the unit cell, we introduce the intra- and interion spin-orbit coupling constants to separate the effect of the related couplings on the band structure and the Fermi surface. Both the intra- and inter-ion parts lift the degeneracy of some bands at the Γ = (0; 0) point and the splitting of bands along the (0; π) - (π; π) direction of the Brillouin zone. We show that the inter-ion part of the spin-orbit coupling leads to the topological change of the Fermi surface — the splitting of two Fermi surface sheets around the M = (π; π) point.