Phase diagram of the two-orbital model for iron-based HTSC: variational cluster approximation

The phase diagram of the two-dimensional two-orbital Hubbard model, which is widely used to describe high-temperature iron-based superconductors, is calculated in the electron doping region using the method of the variational cluster approximation. It is found that the coexistence of the antiferromagnetic and superconducting phases is realized in a wide range of electron doping values. In the superconducting phase, the order parameter has $s^{\pm}$ symmetry.