Evolution of the neutron resonances in AFe ₂Se ₂

Recent experiments on the alkali-intercalated iron selenides have raised questions about the symmetry of the superconducting phase. Random phase approximation calculations of the leading pairing eigenstate for a tight-binding 5-orbital Hubbard-Hund model of AFe ₂Se ₂ find that a d-wave (B _1g) state evolves into an extended s ^± (A _1g) state as the system is hole-doped. However, over a range of doping these two states are nearly degenerate. Here, we calculate the imaginary part of the magnetic spin susceptibility χ ^{′ ′}(q,ω) for these gaps and discuss how the evolution of neutron scattering resonances can distinguish between them.