Polarization-Dependent Three-Dimensional Angle-Resolved Photoemission Spectroscopy of BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$

We performed polarization- and photon-energy-dependent angle-resolved photoemission spectroscopy of a slightly overdoped iron pnictide superconductor, BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$, to clarify the three-dimensional electronic structure including its orbital characters at the Brillouin zone center. Two hole Fermi surfaces (FSs) with $d_{xz\mathrm{/}yz}$ and $d_{xy\mathrm{/}{x}^2-y^2}$ orbitals were observed but $d_{z^2}$ hole FS, which has nodes according to a theory of the spin-fluctuation superconductivity mechanism, did not appear. These results suggest that no node will appear at hole FSs at the zone center.