Multi-orbital Fermi surfaces in metallic layered nickelate

The three-dimensional Fermi surface structure of hole-doped metallic layered nickelate Eu$_{2-x}$Sr$_x$NiO$_4$ ($x=1.1$), an important counterpart to the isostructural superconducting cuprate La$_{2-x}$Sr$_x$CuO$_4$, is investigated by energy-dependent soft-x-ray angle-resolved photoemission spectroscopy. In addition to a large cylindrical hole Fermi surface analogous to the cuprates, we observe a Gamma-centered $3z^2-r^2$-derived small electron pocket. This finding demonstrates that in the layered nickelate the $3z^2-r^2$ band resides close to the $x^2-y^2$ one in energy. The resultant multi-band feature with varying orbital character as revealed may strongly work against the emergence of the high-temperature superconductivity.