The nematicity induced d-symmetry charge density wave in electron-doped iron-pnictide superconductors

The interplay among the nematicity, the stripe spin-density-wave (SDW) order and superconductivity in iron-pnictides is studied in a self-consistent Bogoliubov-de Gennes equations. Our calculations have shown that the nematic-order breaks the degeneracy of d_xz and d_yz orbitals and causes the elliptic Fermi surface near the Γ point in the normal state. In addition, the appearance of the orthorhombic magnetic fluctuations generates two uneven pairs of peaks at (± π 0) and (0, ± π) in its Fourier transformation. All these are comparing favorably with experimental measurements. In the nematic phase, our results indicate that the charge density and its spatial image in the local density of states exhibit a d_x²−y²-like symmetry. Finally, the complete phase diagram is obtained and the nematic phase is found to be in a narrow region close to the SDW transition in the electron-doped iron-pnictide superconductors.