Manousakis, EfstratiosRen, JunMeng, ShengKaxiras, Efthimios2019-09-202008-11-19Manousakis, Efstratios, Jun Ren, Sheng Meng, and Efthimios Kaxiras. 2008. “Effective Hamiltonian for FeAs-Based Superconductors.” Physical Review B 78 (20). https://doi.org/10.1103/physrevb.78.205112.1098-01211550-235Xhttp://nrs.harvard.edu/urn-3:HUL.InstRepos:41384090The 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(x)(2)-y(2) Fe orbital, (b) one spanned by the degenerate atomic Fe orbitals d(xz) and d(yz), anden-USJournal Article2019-09-2010.1103/PhysRevB.78.205112