Absence of a Holelike Fermi Surface for the Iron-BasedK0.8Fe1.7Se2Superconductor Revealed by Angle-Resolved Photoemission Spectroscopy

Abstract

We have performed an angle-resolved photoemission spectroscopy study of the new iron-based superconductor ${\mathrm{K}}_{0.8}{\mathrm{Fe}}_{1.7}{\mathrm{Se}}_2$ ($T_c\sim 30\mathrm{K}$). Clear band dispersion is observed with the overall bandwidth renormalized by a factor of 2.5 compared to our local density approximation calculations, indicating relatively strong correlation effects. Only an electronlike band crosses the Fermi energy, forming a nearly circular Fermi surface (FS) at $M$ ($\pi$, 0). The holelike band at $\Gamma$ sinks $\sim 90\mathrm{meV}$ below the Fermi energy, with an indirect band gap of 30 meV, to the bottom of the electronlike band. The observed FS topology in this superconductor favors ($\pi$, $\pi$) inter-FS scattering between the electronlike FSs at the $M$ points, in sharp contrast to other iron-based superconductors which favor ($\pi$, 0) inter-FS scattering between holelike and electronlike FSs. DOI: http://dx.doi.org/10.1103/PhysRevLett.106.187001 © 2011 American Physical Society