Stabilization of $s$-wave superconductivity through arsenic $p$-orbital hybridization in electron-doped BaFe${}_2$As${}_2$

Abstract

Using random-phase approximation spin-fluctuation theory, we study the influence of the hybridization between iron $d$-orbitals and pnictide $p$-orbitals on the superconducting pairing state in iron-based superconductors. The calculations are performed for a 16-orbital Hubbard-Hund tight-binding model of BaFe${}_2$As${}_2$ that includes the As-$p$ orbital degrees of freedom in addition to the Fe-$d$ orbitals and compared to calculations for a 10-orbital Fe-$d$ only model. In both models we find a leading $s^{\pm }$ pairing state and a subleading $d_{x^2-y^2}$-wave state in the parent compound. Upon doping, we find that the $s^{\pm }$ state remains the leading state in the 16-orbital model up to a doping level of 0.475 electrons per unit cell, at which the hole Fermi surface pockets at the zone center start to disappear. This is in contrast to the 10-orbital model, where the $d$-wave state becomes the leading state at a doping of less than 0.2 electrons. This improved stability of $s^{\pm }$ pairing is found to arise from a decrease of $d_{xy}$ orbital weight on the electron pockets due to hybridization with the As-$p$ orbitals and the resulting reduction of near $(\pi ,\pi )$ spin-fluctuation scattering which favors the competing $d$-wave state. These results show that the orbital dependent hybridization of Fermi surface Bloch states with the usually neglected $p$-orbital states is an important ingredient in an improved itinerant pairing theory.

6 pages, 4 figures

References in corpus (7)

• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides
• d-wave pairing from spin fluctuations in the KxFe{2-y}Se2 superconductors
• Neutron scattering as a probe of the Fe-pnicitide superconducting gap
• Neutron Scattering Resonance and the Fe-pnictide Superconducting Gap
• Muon spin relaxation studies of magnetic order and superfluid density in antiferromagnetic NdOFeAs, BaFe2As2 and superconducting (Ba,K)Fe2As2
• Suppression of superconductivity by Neel-type magnetic fluctuations in the iron pnictides

Cited by in corpus (1)

• Time-reversal symmetry-breaking nematic superconductivity in FeSe