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The discovery of infinite-layer nickelate superconductors has spurred enormous interest. While the Ni$^{1+}$ cations possess nominally the same 3d$^9$ configuration as Cu$^{2+}$ in high-$T_C$ cuprates, the electronic structure consistencies and variances remain elusive, due to the lack of direct experimental probes. Here, we present a soft x-ray photoemission spectroscopy study on both parent and doped infinite-layer Pr-nickelate thin films with a doped perovskite reference. By identifying the Ni character with resonant photoemission and comparison to density function theory + U calculations, we estimate U ~ 5 eV, smaller than the charge transfer energy $Delta$ ~ 8 eV, in contrast to the cuprates being charge transfer insulators. Near the Fermi level (EF), we observe a signature of rare-earth spectral intensity in the parent compound, which is depleted upon doping. The parent compound, self-doped from rare-earth electrons, exhibits higher density of states at EF but manifests weaker superconducting instability than the Sr-doped case, demonstrating a complex interplay between the strongly-correlated Ni 3d and the weakly-interacting rare-earth 5d states in these oxide-intermetallic nickelates.
We report high resolution angle-resolved photoemission spectroscopy (ARPES) studies of the electronic structure of BaFe$_2$As$_2$, which is one of the parent compounds of the Fe-pnictide superconductors. ARPES measurements have been performed at 20 K
We present a soft X-ray angle-resolved photoemission spectroscopy (SX-ARPES) study of the stoichiometric pnictide superconductor LaRu2P2. The observed electronic structure is in good agreement with density functional theory (DFT) calculations. Howeve
The search for oxide materials with physical properties similar to the cuprate high Tc superconductors, but based on alternative transition metals such as nickel, has grown and evolved over time. The recent discovery of superconductivity in doped inf
We have performed soft x-ray and ultrahigh-resolution laser-excited photoemission measurements on tetragonal FeSe, which was recently identified as a superconductor. Energy dependent study of valence band is compared to band structure calculations an
We have performed high-resolution angle-resolved photoemission spectroscopy on the optimally-doped Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ compound and determined the accurate momentum dependence of the superconducting (SC) gap in four Fermi-surface sheets i