Doping dependence of the electronic structure in phosphorus-doped ferropnictide superconductor BaFe2(As1-xPx)2 studied by angle-resolved photoemission spectroscopy

BaFe2(As1-xPx)(2) is a unique iron-based superconductor, where the superconductivity is induced by the isovalent substitution of phosphorus (P) for arsenic (As). Unlike other iron pnictides, the superconducting gap in BaFe2(As1-xPx)(2) has been suggested to contain nodal lines by various experiments. The exact nature of the isovalent doping and nodal gap are key open issues in building a comprehensive picture of the iron-based superconductors. With angle-resolved photoemission spectroscopy, we found that the P substitution in BaFe2(As1-xPx)(2) alters the electronic structure significantly. With P doping, the hole and electron Fermi surface sheets expand simultaneously and the band velocities are enhanced indicating a suppression of electron correlations. Moreover, the P doping induces strong k(z) dispersion on the d(xz)-originated band with significant mixing of the d(z2) orbital around Z, while the d(xy)-originated band and the electron pockets are relatively intact. These rule out theories suggesting that the nodal gap is due to the vanishing d(xy) hole pocket, while support those considering a d(z2)-dominated hole Fermi surface around Z being responsible. Our results are thus helpful to explain the nodal superconductivity in BaFe2(As1-xPx)(2) and understand the role of lattice parameter or pressure effect in iron-based superconductors.