Inelastic neutron scattering on iron-based superconductor BaFe2(As,P)2

Abstract: Inelastic neutron scattering has been performed on powder sample of an iron-based superconductor BaFe2(As0.65P0.35)2 with superconducting transition temperature (T c)=30K, whose superconducting (SC) order parameter is expected to have line node. In the normal state, constant-E scan of dynamical structure factor, S(Q, E), exhibits a peak structure centered at momentum transfer Q ∼1.20Å−1, corresponding to antiferromagnetic wave vector. Below T c, the redistribution of the magnetic spectral weight takes place, resulting in the formation of a peak at E ∼12meV and a gap below 6meV. The enhanced magnetic peak structure is ascribed to the spin resonance mode, evidencing sign change in the SC order parameter similar to other iron-based high-T c superconductors. It suggests that fully-gapped s ± symmetry dominates in this superconductor, which gives rise to high-T c (=30K) despite the nodal symmetry. [Copyright &y& Elsevier]