论文标题
氧气空缺引起的位点选择性Mott在lanio3中的转变
Oxygen vacancy induced site-selective mott transition in lanio3
论文作者
论文摘要
尽管相关材料中的氧空位等缺陷可以大大修改其电子特性，但了解缺陷材料中电子相关性的微观起源是难以捉摸的。带有氧空位的灯笼镍，lanio $ _ {3-x} $，随着氧气空位水平$ x $的增加，从石学计量范围$ _3 $中增加了金属对绝缘体的过渡。特别是，lanio $ _ {2.5} $表现出一个顺磁绝缘阶段，还稳定在$ t_n \ simeq152 $ k以下的反铁磁状态。在这里，我们使用第一原理研究LANIO $ _ {3-X} $的电子结构和能量。我们发现LANIO $ _ {2.5} $稳定了具有绝缘基态的空缺结构，并且绝缘阶段的性质是使用密度功能理论加上动力学均值场理论（DFT+DMFT）获得的“位点选择性”副磁性莫特状态。 Ni八面体位点会形成一个具有很强相关性的Mott绝缘状态，因为Ni $ e_g $轨道是半填充的，而Ni Square-Planar位点带有顶端氧空位，将其变成带绝缘子。我们的氧气空位结果无法通过仅在刚性带移位近似中单独的Ni氧化态的纯变化来解释。我们的DFT+DMFT密度解释说，通过实验X射线吸收光谱测量的LANIO $ _ {3-X} $在LANIO $ _ {3-X} $中的峰值分裂源自空位订购结构中的两个非ni离子。
While defects such as oxygen vacancies in correlated materials can modify their electronic properties dramatically, understanding the microscopic origin of electronic correlations in materials with defects has been elusive. Lanthanum nickelate with oxygen vacancies, LaNiO$_{3-x}$, exhibits the metal-to-insulator transition as the oxygen vacancy level $x$ increases from the stoichiometric LaNiO$_3$. In particular, LaNiO$_{2.5}$ exhibits a paramagnetic insulating phase, also stabilizing an antiferromagnetic state below $T_N\simeq152$K. Here, we study the electronic structure and energetics of LaNiO$_{3-x}$ using first-principles. We find that LaNiO$_{2.5}$ stabilizes a vacancy-ordered structure with an insulating ground state and the nature of the insulating phase is a "site-selective" paramagnetic Mott state as obtained using density functional theory plus dynamical mean field theory (DFT+DMFT). The Ni octahedron site develops a Mott insulating state with strong correlations as the Ni $e_g$ orbital is half-filled while the Ni square-planar site with apical oxygen vacancies becomes a band insulator. Our oxygen vacancy results can not be explained by the pure change of the Ni oxidation state alone within the rigid band shift approximation. Our DFT+DMFT density of states explains that the peak splitting of unoccupied states in LaNiO$_{3-x}$ measured by the experimental X-ray absorption spectra originates from two nonequivalent Ni ions in the vacancy-ordered structure.
