Band Structure And Fermi Surfaces Of The Reentrant Ferromagnetic Superconductor Eu(Fe0.86ir0.14)(2)As-2

The electronic structure of the reentrant superconductor Eu(Fe0.86Ir0.14)(2)As-2 (T-c = 22 K) with coexisting ferromagnetic order (T-M = 18 K) is investigated using angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy. We study the in-plane and out-of-plane band dispersions and Fermi surface (FS) of Eu(Fe0.86Ir0.14)(2)As-2. The near-EF Fe-3d-derived band dispersions near the Gamma and X high-symmetry points show changes due to Ir substitution, but the FS topology is preserved. From momentum-dependent measurements of the superconducting gap measured at T = 5 K, we estimate an essentially isotropic s-wave gap (Delta similar to 5.25 +/- 0.25 meV), indicative of strong-coupling superconductivity with 2 Delta/k(B)T(c) similar or equal to 5.8. The gap gets closed at temperatures T >= 10 K, and this is attributed to the resistive phase which sets in at TM = 18 K due to the Eu2+-derived magnetic order. The modification of the FS with Ir substitution clearly indicates an effective hole doping with respect to the parent compound.