Angle-Resolved Photoemission Observation Of Isotropic Superconducting Gaps In Isovalent Ru-Substituted Ba(Fe0.75ru0.25)(2)As-2

We used high-energy resolution angle-resolved photoemission spectroscopy to extract the momentum dependence of the superconducting gap of Ru-substituted Ba(Fe0.75Ru0.25)(2)As-2 (T-c = 15 K). Despite a strong out-of-plane warping of the Fermi surface, the magnitude of the superconducting gap observed experimentally is nearly isotropic and independent of the out-of-plane momentum. More precisely, we respectively observed 5.7 and 4.5 meV superconducting gaps on the inner and outer Gamma-centered hole Fermi surface pockets, whereas a 4.8 meV gap is recorded on the M-centered electron Fermi surface pockets. Our results are consistent with the J(1)-J(2) model with a dominant antiferromagnetic exchange interaction between the next-nearest Fe neighbors. DOI: 10.1103/PhysRevB.87.094513