Phase diagram of iron pnictides if doping acts as a source of disorder

We obtain and analyze the phase diagram of doped iron pnictides under the assumption that doping adds nonmagnetic impurities to the system but does not change the densities of carriers. We show that the phase diagram is quite similar to the one obtained under the opposite rigid band assumption. In both cases, there is a phase where s ^± superconductivity and antiferromagnetism coexist. We evaluate the jump of the specific heat, ΔC, at the superconducting T _c across the phase diagram and show that ΔC/T _c is nonmonotonic, with the maximum at the onset of the coexistence phase. Our results are in quantitative agreement with experiments on some iron pnictides.