Motivated by the recent x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) experiments, we use a detailed impurity model to explore the nature of the parent compound and hole-doped states of (La, Nd, $\mathrm{Pr}){\mathrm{NiO}}_2$ by including the crystal field splitting, the $\mathrm{Ni}\text{−}3d$ multiplet structure, and the hybridization between $\mathrm{Ni}\text{−}3d, \mathrm{O}\text{−}2p$, and $\mathrm{Nd}\text{−}5d$ orbitals. For simplicity and stimulated by the recent electronic structure calculations, the latter are formally replaced with symmetric orbitals centered at the missing O sites in the Nd layer, forming a two-dimensional band strongly hybridizing with the $\mathrm{Ni}\text{−}3d_{z^2}^9$ state. This hybridization pushes the main part of the $3d_{z^2}^9$ spectral function up in energy by several eV and stabilizes the singlet with considerable $d_{z^2}^9$ and other configurational components. For the parent compound, we find that states of $\mathrm{Ni}\text{−}3d_{z^2}^9$ character spread over a large energy range in the spectra, and cannot and should not be represented by a single orbital energy, as suggested in other approximations. This is qualitatively consistent with the RIXS measurements showing a broad distribution of the $\mathrm{Ni}\text{−}3d_{z^2}^9$ hole state, although the shape of the $\mathrm{Ni}\text{−}3d_{z^2}^9$ related structure is much more complicated requiring reinterpretations of the RIXS data. For the hole-doped systems, we show that adding these additional ingredients can still result in the lowest-energy hole-doped state having a singlet character.

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无限层镍酸盐超导体中单线态空穴掺杂状态的稳定

受最近的 X 射线吸收光谱和共振非弹性 X 射线散射 (RIXS) 实验的启发，我们使用详细的杂质模型来探索母体化合物的性质和 (La, Nd,$\mathrm{公关}){\mathrm{氧化镍}}_2$通过包括晶体场分裂，$你\text{-}3d$多重结构，以及之间的杂交$你\text{-}3d, \mathrm{○}\text{-}2p$， 和$钕\text{-}5d$轨道。为简单起见并受最近电子结构计算的启发，后者正式替换为以 Nd 层中缺失的 O 位点为中心的对称轨道，形成与$你\text{-}3d_{z^2}^9$状态。这种杂交推动了$3d_{z^2}^9$光谱函数的能量增加了几个 eV，并以相当大的速度稳定了单线态$d_{z^2}^9$和其他配置组件。对于母体化合物，我们发现$你\text{-}3d_{z^2}^9$特征分布在光谱中的大能量范围内，不能也不应该用单个轨道能量来表示，正如其他近似值所建议的那样。这在质量上与 RIXS 测量结果一致，显示了广泛分布的$你\text{-}3d_{z^2}^9$孔状态，虽然形状的$你\text{-}3d_{z^2}^9$相关结构要复杂得多，需要重新解释 RIXS 数据。对于空穴掺杂系统，我们表明添加这些额外成分仍然可以导致具有单线态特征的最低能量空穴掺杂状态。