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

TL;DR

This study uses high-resolution photoemission spectroscopy to investigate the superconducting gap and pseudogap in La(O$_{0.93}$F$_{0.07}$)FeAs, revealing deviations from isotropic s-wave symmetry and pseudogap behavior similar to cuprates.

Contribution

It provides the first detailed measurement of the superconducting gap and pseudogap in an iron-based superconductor, highlighting unconventional pairing symmetry.

Findings

Superconducting gap deviates from isotropic s-wave symmetry.

Pseudogap of 15-20 meV observed above Tc.

Pseudogap closes at temperatures well above Tc.

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.