Unconventional superconducting gap in NaFe0.95Co0.05As 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
DOI 10.1103/PhysRevB.84.064519 · Physical Review B
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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.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| NaFe0.95Co0.05As Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 18 | Pressure not reported | unknown |
| LiFeAs Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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