The origin of the electron-hole asymmetry of the spin fluctuation and its effect on superconductivity in iron-based superconductors

We obtain an approximate five orbital model for the 122 iron pnictides, and study its spin fluctuations within the random phase approximation. In particular, we focus on the peak position of the spin fluctuations, and study the origin of its electron-hole asymmetry. The origin of the incommensurate spin fluctuations in the heavily doped materials is found to be essentially the same as that driving the commensurate spin fluctuations in the less doped materials, and the electron-hole asymmetry can be understood from the multiorbital nature of the Fermi surface.