We have performed high-resolution angle-resolved photoemission measurements on superconducting electron-doped NaFe0.95Co0.05As (Tc∼18K). We observed a holelike Fermi surface around the zone center and two electronlike Fermi surfaces around the M point, which can be connected by the Q=(π,π) wave vector, suggesting that scattering over the near-nested Fermi surfaces is important in this 111 pnictide. Nearly isotropic superconducting gaps with sharp coherent peaks are observed below Tc on all three Fermi surfaces. Upon increasing temperature through Tc, the gap size shows little change while the coherence vanishes. Large ratios of 2Δ/kBTc∼8 are observed for all the bands, indicating a strong coupling in this system. These results are not expected from a classical phonon-mediated pairing mechanism.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2011 Aug 23|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics