Superconducting Gap and Pseudogap in Iron-Based Layered Superconductor La(O${}_{1-x}$F${}_x$)FeAs

Abstract

We report high-resolution photoemission spectroscopy of newly-discovered iron-based layered superconductor La(O${}_{0.93}$F${}_{0.07}$)FeAs (Tc = 24 K). We found that the superconducting gap shows a marked deviation from the isotropic s-wave symmetry. The estimated gap size at 5 K is 3.6 meV in the s- or axial p-wave case, while it is 4.1 meV in the polar p- or d-wave case. We also found a pseudogap of 15-20 meV above Tc, which is gradually filled-in with increasing temperature and closes at temperature far above Tc similarly to copper-oxide high-temperature superconductors.

4 pages, 3 figures, J. Phys. Soc. Jpn. Vol. 77, No. 6 (2008), in press

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