The Nodal SDW Gap and the Superconducting Gap in BaFe2−x Co x As2

Abstract

The spin density wave (SDW) transition in BaFe2As2 and the superconducting transition in BaFe1.84Co0.16As2 were investigated by Raman scattering. The symmetries of the nodal SDW gap at 400 cm−1 and the superconducting gap at 75 cm−1 are both B2g. The superconducting coherent peak energy is smaller than the gap energy of the hole pocket, indicating that the peak is the resonant peak in the S± superconductor. The superconducting symmetry is given by B2g in the orbital combination and A1g (S±) in the momentum space. The exchange interaction energies are estimated from the two-magnon peak.