Q-scan-analysis of the neutron scattering in iron-based superconductors

We propose a way to determine the pairing state of the iron pnictide superconductors exploiting the momentum (Q) scan of the neutron scattering data. We investigate the spin susceptibility in the s+- and s++ superconducting states for various doping levels using the effective five-orbital model and considering the quasiparticle damping. The peak position of the intensity shifts from the position on the line Qx = pi to that on the line Qy = 0 as the doping level is decreased from electron doping to hole doping. We find that the Q-dependence of the ratio of the intensity in the superconducting state to that in the normal state is qualitatively different between the s+- -wave and s++ -wave pairings. We propose to investigate experimentally this ratio in Q-space to distinguish the two pairing states.