Flat band in twisted bilayer Bravais lattices
Flat band in twisted bilayer Bravais lattices
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DOI：
10.1103/physrevresearch.1.033076
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发表时间：
2019-11-05
影响因子：
4.2
通讯作者：
Vishwanath, Ashvin
中科院分区：
文献类型：
--
作者：
Kariyado, Toshikaze;Vishwanath, Ashvin
在扭曲的双层的五个通用的二维布拉菲网络的能带工程进行了演示。我们首先推导出层间耦合的约束，确定了一个有效的潜在的低能量物理。约束源于对称性，并在不涉及微观细节的情况下固定。对电势的约束有助于我们预测和理解电子在莫尔结构影响下的行为，如平带的形成。它还指出，通用的约束成为最相关的微观层间耦合的典型长度尺度时，是温和的。这些概念在简单的紧束缚模型中进行了数值测试，显示出与通用约束固定的潜在轮廓兼容的带平坦化。在一般理论的基础上，我们提出了各向异性带平坦化的可能性，其中准一维带色散是从相对各向同性的原始带色散产生的。在强关联区，各向异性能带平坦化导致自旋轨道模型，其中交织的磁性和轨道有序可以产生丰富的物理。总体而言，我们的理论和示范提供了有用的信息，筛选出感兴趣的材料从材料数据库。
Band engineering in twisted bilayers of the five generic two-dimensional Bravais networks is demonstrated. We first derive constraints on the interlayer coupling that determines an effective potential for low-energy physics. The constraints are originated from symmetry and fixed without reference to microscopic details. Having the constraints on the potential helps us to predict and understand electron behavior under the influence of the moire structure, like formation of flat bands. It is also pointed out that the generic constraints become most relevant when the typical length scale of the microscopic interlayer coupling is moderate. The concepts are numerically tested in simple tight-binding models, showing the band flattening compatible with the potential profile fixed by the generic constraints. On the basis of the generic theory, we propose a possibility of anisotropic band flattening, in which quasi-one-dimensional band dispersion is generated from relatively isotropic original band dispersion. In the strongly correlated regime, the anisotropic band flattening leads to a spin-orbital model where intertwined magnetic and orbital ordering can give rise to rich physics. Overall, our theory and demonstration give useful information for screening out interesting materials from the material database.