2008/06/30 by Efstratios Manousakis, Jun Ren, Junfeng Ren +2 · 1 citation
Materials Science · Physics and Astronomy · #Iron-based superconductors research #Physics of Superconductivity and Magnetism #Rare-earth and actinide compounds #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.78.205112
published as Phys. Rev. B 78, 205112 (2008) · 11 pages, 6 figures
openalex publication_date 2008/11/19 · arxiv created 2008/11/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
The recently discovered FeAs-based superconductors show intriguing behavior and unusual dynamics of electrons and holes which occupy the Fe d orbitals and As 4s and 4p orbitals. Starting from the atomic limit, we carry out a strong-coupling expansion to derive an effective Hamiltonian that describes the electron and hole behaviors. The hopping and the hybridization parameters between the Fe d and As s and p orbitals are obtained by fitting the results of our density-functional-theory calculations to a tight-binding model with nearest-neighbor interactions and a minimal orbital basis. We find that the effective Hamiltonian, in the strong on-site Coulomb-repulsion limit, operates on three distinct subspaces coupled through Hund's rule. The three subspaces describe different components (or subsystems): (a) one spanned by the d_x2\ensuremath-y2 Fe orbital, (b) one spanned by the degenerate atomic Fe orbitals dxz and dyz, and (c) one spanned by the atomic Fe orbitals dxy and d_z2. Each of these Hamiltonians is an extended t\ensuremath-t^\ensuremath'\ensuremath-J\ensuremath-J^\ensuremath' model and is characterized by different coupling constants and filling factors. For the case of the undoped material the second subspace alone prefers a ground state characterized by a spin-density-wave order similar to that observed in recent experimental studies, while the other two subspaces prefer an antiferromagnetic order. We argue that the observed spin-density-wave order minimizes the ground-state energy of the total Hamiltonian.