Study of the magnetic state of K0.8Fe1.6Se2 from a five-orbital Hubbard model in the Hartree-Fock approximation

QINLONG LUO; ANDREW NICHOLSON; JOSE RIERA; DAO-XIN YAO; ADRIANA MOREO; ELBIO DAGOTTO

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2011 vol. 84 p. 1405061 - 1405064

1098-0121

Motivated by the recent discovery of Fe-based superconductors close to an antiferromagnetic insulator in the experimental phase diagram, here the five-orbital Hubbard model (without lattice distortions) is studied using the real-space Hartree-Fock approximation, employing a 10 × 10 Fe cluster with Fe vacancies in a √5 ×√5 pattern. Varying the Hubbard and Hund couplings, and at electronic density n = 6.0, the phase diagram contains an insulating state with the same spin pattern as observed experimentally, involving 2 × 2 ferromagnetic plaquettes coupled with one another antiferromagnetically. The presence of local ferromagnetic tendencies is in qualitative agreement with Lanczos results for the three-orbital model also reported here. The magnetic moment∼3μB/Fe isin good agreement with experiments. Several other phases are also stabilized in the phase diagram, in agreement with recent calculations using phenomenological models.