A BCS-like gap in the superconductor SmFeAsO0.85F0.15

T. Y. Chen, Z. Tesanovic, R. H. Liu, X. H. Chen, C. L. Chien

Research output: Contribution to journalArticle

278 Scopus citations

Abstract

Since the discovery of superconductivity in the high-transition-temperature (high-Tc) copper oxides two decades ago, it has been firmly established that the CuO2 plane is essential for superconductivity and gives rise to a host of other very unusual properties. A new family of superconductors with the general composition of LaFeAsO1-xF x has recently been discovered and the conspicuous lack of the CuO2 planes raises the tantalizing question of a different pairing mechanism in these oxypnictides. The superconducting gap (its magnitude, structure, and temperature dependence) is intimately related to pairing. Here we report the observation of a single gap in the superconductor SmFeAsO 0.85F0.15 with Tc = 42 K as measured by Andreev spectroscopy. The gap value of 2Δ = 13.34 ± 0.3 meV gives 2Δ/kBTc = 3.68 (where kB is the Boltzmann constant), close to the Bardeen-Cooper-Schrieffer (BCS) prediction of 3.53. The gap decreases with temperature and vanishes at Tc in a manner consistent with the BCS prediction, but dramatically different from that of the pseudogap behaviour in the copper oxide superconductors. Our results clearly indicate a nodeless gap order parameter, which is nearly isotropic in size across different sections of the Fermi surface, and are not compatible with models involving antiferromagnetic fluctuations, strong correlations, the t-J model, and the like, originally designed for the high-Tc copper oxides.

Original languageEnglish (US)
Pages (from-to)1224-1227
Number of pages4
JournalNature
Volume453
Issue number7199
DOIs
StatePublished - Jun 26 2008

    Fingerprint

ASJC Scopus subject areas

  • General

Cite this

Chen, T. Y., Tesanovic, Z., Liu, R. H., Chen, X. H., & Chien, C. L. (2008). A BCS-like gap in the superconductor SmFeAsO0.85F0.15. Nature, 453(7199), 1224-1227. https://doi.org/10.1038/nature07081