Phase diagram of doped BaFe₂As₂ superconductor under broken C₄ symmetry

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We develop a minimal multiorbital tight-binding model with realistic hopping parameters. The model breaks the symmetry of the tetragonal point group by lowering it from C₄ to D₂d, which accurately describes the Fermi surface evolution of the electron-doped BaFe₂₋ₓCoₓAs₂ and hole-doped Ba₁₋yKyFe₂As₂ compounds. An investigation of the phase diagram with a mean-field t-U-V Bogoliubov-de Gennes Hamiltonian results in agreement with the experimentally observed electron- and hole-doped phase diagram with only one set of t, U and V parameters. Additionally, the self-consistently calculated superconducting order parameter exhibits s±-wave pairing symmetry with a small d-wave pairing admixture in the entire doping range, % The superconducting s± + d-wave order parameter which is the subtle result of the weakly broken symmetry and competing interactions in the multiorbital mean-field Hamiltonian.