Spin density wave in oxypnictide superconductors in a three-band model

Abstract

The spin density wave and its temperature dependence in oxypnictide are studied in a threeband model. The spin susceptibilities with various interactions are calculated in the random phase approximation(PPA). It is found that the spin susceptibility peaks around the M point show a spin density wave(SDW) with momentum (0, π) and a clear stripe-like spin configuration. The intraband Coulomb repulsion enhances remarkably the SDW but the Hund's coupling weakens it. It is shown that a new resonance appears at higher temperatures at the Γ point indicating the formation of a paramagnetic phase. There is a clear transition from the SDW phase to the paramagnetic phase.

Magnetic order in orbital models of the iron pnictides

“…86 We note that there are several alternative three-orbital models which display an xy-dominated hole pocket at the M point. 44,53 A similar analysis to that performed here has been carried out for such a three-orbital model, 62 and the susceptibility was found to be peaked at an incommensurate wavevector close to (π, 0). More recently, Zhou and Wang studied a three-orbital model of LaFeAsO using Gutzwiller mean-field theory restricted to two-site magnetic unit cells and found significant deviations from the usual Hartree-Fock approach.…”

Influence of multi-orbital hopping and anisotropy in intra and inter orbital Coulomb interactions on the electronic spectra in iron pnictide superconductors

“…The various theoretical attempts have been made based on the two orbital [29][30][31][32]33], three orbital [19,20,34,35] and also five 3d orbital per site models [36]. Recently, we have theoretically analyzed the spectral function of electronic states within two orbital per site tight binding model for iron pnictide superconductors and pointed out that the Hund's coupling term accumulate the spectral weight (i.e.…”

“…It is pointed out that band renormalization is anisotropic due to Coulomb interaction and dominated by orbital physics close to (0, p) point. Long et al [35] found that in iron based system at the (0, p) point, spin density wave (SDW) peak enhanced due to the intra-orbital Coulomb interaction, while it reduced with Hund's coupling energy. Therefore, the onsite intra and inter-orbital Coulomb interactions and Hund's coupling energy play an essential role in understanding the physics of multi-orbital in superconducting state of iron pnictide/chalcogenide systems.…”

“…Therefore, in the light of above ARPES data [17] and theoretical attempts [19,20,34,35], the influence of Fe 3d multi-orbital couplings, intra-orbital and inter-orbital electronic interactions and Hund's coupling term on the electronic spectra need to be analyzed properly in iron based superconductors. Hence, in the present work, we attempt the three orbital per site model Hamiltonian (a manifestation of three overlapping Fe 3d-orbitals per sites i.e.…”

“…d xz , d yz and d xy ) for iron pnictide superconductors within BCS mean field scenario in order to maintain self-consistency. The theoretically obtained spectral function of electronic states has been numerically analyzed as a function of various model parameters by employing Green's function formalism and compared with the existing ARPES data [16] and other available theoretical investigations [19,20,35] related to electronic spectra in iron pnictide superconductors. We have taken into account the extended s-wave (D ak = D 0 cos(k x )cos(k y )) pairing symmetry in superconducting state of iron pnictides as proposed by several workers [33,34,[37][38][39][40][41][42].…”