Insulating band gaps both below and above the Néel temperature in d-electron LaTiO3 , LaVO3 , SrMnO3 , and LaMnO3 perovskites as a symmetry-breaking event
Insulating band gaps both below and above the Néel temperature in d-electron LaTiO3 , LaVO3 , SrMnO3 , and LaMnO3 perovskites as a symmetry-breaking event
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d 电子 LaTiO3、LaVO3、SrMnO3 和 LaMnO3 钙钛矿中低于和高于尼尔温度的带隙绝缘，作为对称性破缺事件
DOI：
10.1103/physrevmaterials.7.074406
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发表时间：
2023
影响因子：
3.4
通讯作者：
Zunger, Alex
中科院分区：
文献类型：
--
作者：
Malyi, Oleksandr I.;Zhao, Xin-Gang;Zunger, Alex
每个细胞具有奇数个电子的金属电子氧化物在费米能级下应表现出能带简并性，这使得它们在能带理论中正式具有金属性。然而，在许多情况下，这些都是假金属，这一点可以通过观察发现具有磁性 B 原子的多氧化物钙钛矿在低于和高于尼尔温度时都是绝缘体来证明。历史上，实验观察与预期之间的这些不一致是通过调用破坏简并的物理学来解决的，这主要基于纯电子效应，例如电子化合物的强电子间相关性（莫特机制）。这种解释通常认为微观晶格或磁自由度（m-DOF）在很大程度上是被动的旁观者，而不是正式金属成为绝缘体的原因。然而，人们早就知道钙钛矿可以以八面体倾斜、键二聚、Jahn-Teller 畸变和局部磁矩排序的形式表现出 m-DOF 的排列。需要允许这种结构和磁局部自由度与纯电子强相关性竞争，这似乎是合理的。为了回答这个问题，我们探索了一系列电子氧化物钙钛矿，其原型分别为 1、2、3 或 4 个电子。使用类平均场电子结构方法（此处为密度泛函理论），我们发现磁对称破缺（SB）与结构畸变的结合可以解释该系列中的绝缘带隙，同时正确预测控制情况，即固有的顺磁金属，因为 SB 的强度不足以消除简并性。这表明，在晶胞中定量计算局部磁性和位置 SB 基序，避免从一开始就对低对称性基序进行平均，可以在没有 MottU 的情况下提供莫特转变的一致趋势。
Metal-electron oxides having an odd number of electrons per cell should exhibit band degeneracy at the Fermi energy, making them, in band theory, formally metallic. In many cases, however, these are false metals, as evidenced by the observation that manyoxide perovskites with a magneticB atom are observed to be insulators both below and above the Néel temperature. These inconsistencies between experimental observation and expectation have historically been resolved by invoking degeneracy-breaking physics, based largely on pure electron effects, such as strong interelectronic correlation for-electron compounds (the Mott mechanism). Such explanations generally consider the microscopic lattice or magnetic degrees of freedom (m-DOFs) as largely passive spectators, not causes of the formal metal being an insulator. However, it has long been known thatperovskites can manifest an arrangement of m-DOFs in the form of octahedral tilting, bond dimerization, Jahn-Teller distortions, and ordering of local magnetic moments. It appears reasonable that such structural and magnetic local degrees of freedom need to be allowed to compete with purely electronic strong correlation. To answer this question, we explored a range of-electron oxide perovskites exemplified by the archetypes,,, andwith 1, 2, 3, or 4electrons, respectively. Using a mean-field-like electronic structure method (here, density functional theory), we find that a combination of magnetic symmetry breaking (SB) with structural distortions can account for insulating band gaps in this series while correctly predicting for the control case, an intrinsic paramagnetic metal in, as SB is insufficiently strong to remove the degeneracy. This indicates that calculating quantitatively local magnetic and positional SB motifs in unit cells that avoid averaging at the outset over the low-symmetry motifs can provide consistent trends in a Mott transition without MottU.