论文标题
在绝缘单层杯形和镍盐中共存的激子状态的景观
Landscape of coexisting excitonic states in the insulating single-layer cuprates and nickelates
论文作者
论文摘要
我们提出了一个$ \ textit {ab intio} $研究原型高温超导体LA $ _2 $ cuo $ _4 $的激发态状态，并将它们与等值性的单层单层镍镍$ _2 $ _2 $ nio $ _4 $ _4 $ _4 $。低能电子结构的关键差异会导致截然不同的激发行为。 la $ _2 $ cuo $ _4 $的激子被定位，可以在Cuo $ _2 $飞机中自由移动而不会干扰反铁磁命令。相比之下，在la $ _2 $ nio $ _4 $中，我们发现低洼的激子状态非常局部，产生了几乎平坦的分散体。理论上获得的激子分散和行为与RIX的观察非常吻合。为了对激子进行分类，我们将电子孔耦合投射到每个原子位点，包括原子轨道的完整歧管。我们发现激子由激子类的线性组合组成，包括Mott-Hubbard，$ d-d $和Charge-Transfer。还讨论了这些激励对高$ T_C $配对机制的影响。
We present an $\textit{ab initio}$ study of the excitonic states of a prototypical high-temperature superconductor La$_2$CuO$_4$ and compare them to the isostructural single-layer nickelate La$_2$NiO$_4$. Key difference in the low-energy electronic structure leads to very different excitonic behavior. Excitons in La$_2$CuO$_4$ are delocalized and can freely move in the CuO$_2$ plane without disturbing the antiferromagnetic order. In contrast, in La$_2$NiO$_4$ we find the low-lying excitonic states to be extremely localized, producing a nearly flat dispersion. The theoretically obtained excitonic dispersion and behavior are in excellent agreement with RIXS observations. To classify the excitons we project the electron-hole coupling onto each atomic site including the full manifold of atomic orbitals. We find the excitons to be composed of a linear combination of exciton classes, including Mott-Hubbard, $d-d$, and charge-transfer. The implication of these excitations to the high-$T_c$ pairing mechanism is also discussed.
