Nodal spin density wave in iron-based superconductors

We analyze the competition of SDW and SC orders in the iron-based superconductors, taking into account the orbital matrix elements. We find that the SDW order necessarily possesses the nodal structure as a result of angular dependence of the Fermi-liquid interactions. To obtain the phase diagram we solve the system of coupled mean-field gap equations, which describes the competition between SDW and s++ or s+- superconductivity. We revisit the result, obtained previously, for the constant SDW gap. We further discuss the role played by the spin-orbit coupling.