Band structure, Fermi surface, and superconducting gap in FeAs-based superconductors revealed by angle-resolved photoemission spectroscopy

Abstract

In this paper, we present a brief review on our angle-resolved photoemission measurements on the band structure, Fermi surface, and superconducting gap of the newly-discovered FeAs-based high temperature superconductors. (1) The Fermi surface of the FeAs-based compounds are characterized by the hole-like Fermi surface sheets near Γ (0, 0) and the existence of singular Fermi spots near M (tp, π). However, the origin of the Fermi spots in the magnetically-ordered state of the parent compound BaFe2As2 and optimally-doped (Ba0.6K0.4)Fe2As2 superconductor may be different. (2) The magnetically-ordered state in the parent compound, BaFe2As2, shows unusual electronic signatures that are distinct from the conventional spin-density-wave system. (3) Multiple nodeless superconducting gap has been observed in (Ba0.6K0.4)Fe2As2 superconductor which is consistent with s-wave superconducting order parameter.