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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 Ρ substitution in BaFe2(As1-xPx)2 alters the electronic structure significantly. With Ρ doping, the hole and electron Fermi surface sheets expand simultaneously and the band velocities are enhanced indicating a suppression of electron correlations. Moreover, the Ρ doping induces strong kz dispersion on the dxz-originated band with significant mixing of the dz2 orbital around Z, while the dxy-originated band and the electron pockets are relatively intact. These rule out theories suggesting that the nodal gap is due to the vanishing dxy hole pocket, while support those considering dz2-dominated hole Fermi surface around Ζ 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. [ABSTRACT FROM AUTHOR]

The in-plane resistivity anisotropy has been studied with the Montgomery method on the detwinned parent compound of the iron-based superconductor FeTe. The observed resistivity in the antiferromagnetic (AFM) direction is larger than that in the ferromagnetic (FM) direction, which is different from that observed in BaFe2As2 before. We show that the opposite resistivity anisotropy behavior in FeTe could be attributed to the strong Hund's rule coupling effects, which should be understood in a localized picture: Hund's rule coupling makes hopping along the FM direction easier than along the AFM direction in FeTe, similar to the colossal magnetoresistance observed in some manganites. [ABSTRACT FROM AUTHOR]

We studied the low-lying electronic structure of the newly discovered iron-platinum-arsenide superconductor, Ca10(Pt4As8)(Fe2-xPtxAs2)5 (Tc = 22 K) with angle-resolved photoemission spectroscopy. We found that the Pt4As8 layer contributes to a small electronlike Fermi surface, indicative of metallic charge reservoir layers that are rare for iron based superconductors. Moreover, the electronic structure of the FeAs layers resembles those of other prototype iron pnictides to a large extent. However, there is only dxz-orbital originated holelike Fermi surface near the zone center, which is rather strange for an iron pnictide superconductor with relatively high superconducting transition temperature; and the dxz and dyz originated bands are not degenerate at the zone center. Furthermore, all bands near the Fermi energy show negligible kz dependence, indicating the strong two-dimensional nature of this material. Our results indicate this material possesses a rather interesting electronic structure, which enriches our current knowledge of iron based superconductors. [ABSTRACT FROM AUTHOR]