Band structure and Fermi surfaces of the reentrant ferromagnetic superconductor Eu(Fe0.86Ir0.14)2As2

The electronic structure of the reentrant superconductor Eu(Fe0.86Ir0.14)2As2 (Tc=22 K) with coexisting ferromagnetic order (TM=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)2As2. The near-EF Fe-3d-derived band dispersions near the Γ 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 (Δ∼5.25±0.25 meV), indicative of strong-coupling superconductivity with 2Δ/kBTc≃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.