论文标题
无限层镍的不同电型性质以及计算其电子结构的理论挑战
Distinct electridelike nature of infinite-layer nickelates and the resulting theoretical challenges to calculate their electronic structure
论文作者
论文摘要
我们在本文中证明，最近发现的无限层（IL）镍盐与称为电气的一类材料有很多共同点。基于氧化物的电气是化合物，在该化合物中，拓扑束缚的氧气叶在空隙后面，具有具有吸引力的电子电位的景观。 We show that this is also what happens in the IL nickelates, where one of the two electrons (per formula unit) freed during the topotactic synthesis is to a large degree located in the oxygen vacancy position, occupying partially a local $s$-symmetry interstitial orbital, rather than taking part alongside the other electon in converting Ni from 3+ to a full 1+ oxidation state. We demonstrate that the interstitial orbital in question, referred to by us as the zeronium $s$ or Z $s$ orbital, forms strong covalent bonds with neighboring Ni $3d_{3z^2-r^2}$ orbitals, which in turn facilitates the one-dimensional-like dispersion of the Ni $3d_{3z^2-r^2}$ band along the $c$-axis方向，导致Ni磁矩之间可能发生的大面积耦合。通过我们的电子定位函数分析加强了这一发现，这表明镍和结构类似的蛋饼之间的基本区别可能解释了氢贫困样品中没有超导性的，并且肯定与观察到的大$ z $ z $ z $ z $ z $ z $ z $ z $ al的ni $ l_3 $ l_3 $ l_3 $ -Edge x-ray吸收光谱。此外，通过使用DFT+U计算作为说明，我们表明IL镍的电气样性质是确定这些新型超导体的备受争议的难以捉摸的Fermi表面的理论困难的主要原因之一，而ASLO则在探索它们在低温下探索它们成为兴奋的可能性。
We demonstrate in this paper that the recently discovered infinite-layer (IL) nickelates have much in common with a class of materials known as electrides. Oxide based electrides are compounds in which topotactic removal of loosely bound oxygens leaves behind voids with a landscape of attractive potentials for electrons. We show that this is also what happens in the IL nickelates, where one of the two electrons (per formula unit) freed during the topotactic synthesis is to a large degree located in the oxygen vacancy position, occupying partially a local $s$-symmetry interstitial orbital, rather than taking part alongside the other electon in converting Ni from 3+ to a full 1+ oxidation state. We demonstrate that the interstitial orbital in question, referred to by us as the zeronium $s$ or Z $s$ orbital, forms strong covalent bonds with neighboring Ni $3d_{3z^2-r^2}$ orbitals, which in turn facilitates the one-dimensional-like dispersion of the Ni $3d_{3z^2-r^2}$ band along the $c$-axis direction, leading also to a possible large out-of-plane coupling between Ni magnetic moments. This finding, reinforced by our electron localization function analysis, points to a fundamental distinction between the nickelates and the structurally analogous cuprates, may explain the absence of superconductivity in hydrogen-poor samples, and is certainly in agreement with the observed large $z$-polarized component in the Ni $L_3$-edge x-ray absorption spectra. In addition, by using DFT+U calculations as an illustration, we show that the electride-like nature of the IL nickelates is one of the main reasons for the theoretical difficulty in determining the much debated elusive Fermi surface of these novel superconductors and aslo in exploring the possibility of them becoming excitonic insulators at low temperatures.
