Ab initio derivation of low-energy model for iron-based superconductors LaFeAsO and LaFePO

Kazuma Nakamura, Ryotaro Arita, Masatoshi Imada

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112 Citations (Scopus)

Abstract

Effective Hamiltonians for LaFeAsO and LaFePO are derived from the downfolding scheme based on first-principles calculations and provide insights for newly discovered superconductors in the family of LnFeAsO 1-xFx, Ln = La, Ce, Pr, Nd, Sm, and Gd. Extended Hubbard Hamiltonians for five maximally localized Wannier orbitals per Fe are constructed dominantly from five-fold degenerate iron-3d bands. They contain parameters for effective Coulomb and exchange interactions screened by the polarization of other electrons away from the Fermi level. The onsite Coulomb interaction estimated as 2.2 - 3.3 eV is compared with the transfer integrals between the nearest-neighbor Fe-3d Wannier orbitals, 0.2 -0.3 eV, indicating moderately strong electron correlation. The Hund's rule coupling is found to be 0.3- 0.6 eV. The derived model offers a firm basis for further studies on physics of this family of materials. The effective models for As and P compounds turn out to have very similar screened interactions with slightly narrower bandwidth for the As compound.

Original languageEnglish
Article number093711
JournalJournal of the Physical Society of Japan
Volume77
Issue number9
DOIs
Publication statusPublished - 2008 Sep 1
Externally publishedYes

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Keywords

  • Constrained RPA method
  • Downfolding
  • Effective Hamiltonian
  • First-principles calculation
  • High-temperature superconductivity
  • LaFeAsO
  • LaFePO
  • Oxypnictide

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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