Effect of Orbital Nematicity on Superconductivity in the Iron Pnictides and Chalcogenides

Orbital ordering leading to the observed nematic phase in the iron-based superconductors has been firmly established in a variety of experiments. It is therefore important to investigate the effect of the orbital order on the superconductivity. To this end, we have performed strong-coupling calculation within the slave-boson approach to the multiorbital $t$-$J_1$-$J_2$ models for the iron-based superconductors. We report the phase diagram as a function of both electron/hole doping and the orbital ordering strength. We find that the amplitude of the otherwise dominant $A_{1g}$ ($s\pm$) pairing channel diminishes as the strength of orbital ordering is increased, yielding to the $B_{1g}$ ($d_{x^2-y^2}$) pairing channel. This effect is especially pronounced in the electron-doped case, with the $d$-wave pairing stabilized by the realistic values of the orbital splitting $\sim 50$ meV. While the $d$-wave pairing has not been conclusively observed in the iron-based superconductors, the competition between the $s$- and $d$-wave pairing found in the calculations may have ramifications for FeSe, KFe$_2$As$_2$ and K$_x$Fe$_{2-y}$Se$_2$.