Unconventional superconducting gap in NaFe0.95Co 0.05As observed by angle-resolved photoemission spectroscopy

Z. H. Liu, P. Richard, K. Nakayama, G. F. Chen, S. Dong, J. B. He, D. M. Wang, T. L. Xia, K. Umezawa, T. Kawahara, S. Souma, T. Sato, T. Takahashi, T. Qian, Yaobo Huang, Nan Xu, Yingbo Shi, H. Ding, S. C. Wang

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72 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number064519
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume84
Issue number6
DOIs
Publication statusPublished - 2011 Aug 23

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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