Cui Bin, Zheng Xingwen, Wang Jianfeng, Liu Desheng, Xie Shijie, Huang Bing
School of Physics, National Demonstration Center for Experimental Physics Education, Shandong University, Jinan, 250100, China.
Beijing Computational Science Research Center, Beijing, 100193, China.
Nat Commun. 2020 Jan 2;11(1):66. doi: 10.1038/s41467-019-13794-y.
Lieb lattice has been predicted to host various exotic electronic properties due to its unusual Dirac-flat band structure. However, the realization of a Lieb lattice in a real material is still unachievable. Based on tight-binding modeling, we find that the lattice distortion can significantly determine the electronic and topological properties of a Lieb lattice. Importantly, based on first-principles calculations, we predict that the two existing covalent organic frameworks (COFs), i.e., spC-COF and spN-COF, are actually the first two material realizations of organic-ligand-based Lieb lattice. Interestingly, the spC-COF can experience the phase transitions from a paramagnetic state to a ferromagnetic one and then to a Néel antiferromagnetic one, as the carrier doping concentration increases. Our findings not only confirm the first material realization of Lieb lattice in COFs, but also offer a possible way to achieve tunable topology and magnetism in organic lattices.
由于其独特的狄拉克平带结构，预计利布晶格会呈现出各种奇异的电子特性。然而，在实际材料中实现利布晶格仍然是无法做到的。基于紧束缚模型，我们发现晶格畸变能显著决定利布晶格的电子和拓扑性质。重要的是，基于第一性原理计算，我们预测现有的两种共价有机框架（COF），即spC-COF和spN-COF，实际上是基于有机配体的利布晶格的前两种材料实现形式。有趣的是，随着载流子掺杂浓度的增加，spC-COF会经历从顺磁态到铁磁态再到奈尔反铁磁态的相变。我们的发现不仅证实了COF中利布晶格的首次材料实现，还提供了一种在有机晶格中实现可调拓扑和磁性的可能途径。
