Spin fluctuations and superconductivity in a 3D tight-binding model for BaFe2As2

Abstract

Despite the wealth of experimental data on the Fe-pnictide compounds of the KFe2As2-type, K = Ba, Ca, or Sr, the main theoretical work based on multiorbital tight-binding models has been restricted so far to the study of the related 1111 compounds. This can be ascribed to the more three dimensional electronic structure found by ab initio calculations for the 122 materials, making this system less amenable to model development. In addition, the more complicated Brillouin zone (BZ) of the body-centered tetragonal symmetry does not allow a straightforward unfolding of the electronic band structure into an effective 1Fe/unit cell BZ. Here we present an effective 5-orbital tight-binding fit of the full DFT band structure for BaFeAs including the kz dispersions. We compare the 5-orbital spin fluctuation model to one previously studied for LaOFeAs and calculate the RPA enhanced susceptibility. Using the fluctuation exchange approximation to determine the leading pairing instability, we then examine the differences between a strictly two dimensional model calculation over a single kz cut of the BZ and a completely three dimensional approach. We find pairing states quite similar to the 1111 materials, with generic quasi-isotropic pairing on the hole sheets and nodal states on the electron sheets at kz = 0 which however are gapped as the system is hole doped. On the other hand, a substantial kz dependence of the order parameter remains, with most of the pairing strength deriving from processes near kz = pi. These states exhibit a tendency for an enhanced anisotropy on the hole sheets and a reduced anisotropy on the electron sheets near the top of the BZ.

12 pages, 15 figures

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Cited by in corpus (15)

• d-wave pairing from spin fluctuations in the KxFe{2-y}Se2 superconductors
• Symmetry of spin excitation spectra in the tetragonal paramagnetic and superconducting phases of 122-ferropnictides
• Incommensurate spin-density wave order in electron-doped BaFe2As2 superconductors
• Possible three dimensional nodes in the $s\pm$ superconducting gap of BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Theory for Magnetism and Triplet Superconductivity in LiFeAs
• Pinpointing Gap Minima in Ba(Fe${}_{0.94}$Co${}_{0.06}{)}_2$As${}_2$ \textit{via} Band Structure Calculations and Electronic Raman Scattering
• Anisotropic quasiparticle lifetimes in Fe-based superconductors
• Graphene, Lattice QFT and Symmetries
• Two energy scales in the magnetic resonance spectrum of electron and hole doped pnictide superconductors
• Electronic structure of BaNi${}_2$As${}_2$
• Nodes vs. minima in the energy gap of iron-pnictides from field-induced anisotropy
• Anisotropic Superconducting Properties of Optimally Doped BaFe${}_2$(As${}_{0.65}$P${}_{0.35}$)${}_2$ under Pressure
• ${}^{75}$As NMR of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ in High Magnetic Field
• Determination of the pairing state in iron-based superconductors through neutron scattering
• Observation of a ubiquitous three-dimensional superconducting gap function in optimally-doped Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$