A Lieb-like lattice in a covalent-organic framework and its Stoner ferromagnetism.,Nature Communications

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A Lieb-like lattice in a covalent-organic framework and its Stoner ferromagnetism.
Nature Communications ( IF 14.7 ) Pub Date : 2019-05-17 , DOI: 10.1038/s41467-019-10094-3
Wei Jiang _{1,

2} , Huaqing Huang ₁ , Feng Liu _{1,

3}

Affiliation

Lieb lattice has been extensively studied to realize ferromagnetism due to its exotic flat band. However, its material realization has remained elusive; so far only artificial Lieb lattices have been made experimentally. Here, based on first-principles and tight-binding calculations, we discover that a recently synthesized two-dimensional sp2 carbon-conjugated covalent-organic framework (sp2c-COF) represents a material realization of a Lieb-like lattice. The observed ferromagnetism upon doping arises from a Dirac (valence) band in a non-ideal Lieb lattice with strong electronic inhomogeneity (EI) rather than the topological flat band in an ideal Lieb lattice. The EI, as characterized with a large on-site energy difference and a strong dimerization interaction between the corner and edge-center ligands, quenches the kinetic energy of the usual dispersive Dirac band, subjecting to an instability against spin polarization. We predict an even higher spin density for monolayer sp2c-COF to accommodate a higher doping concentration with reduced interlayer interaction.

中文翻译：

共价有机框架中的利勃样格子及其斯托纳铁磁性。

Lieb晶格因其奇异的平坦带而被广泛研究以实现铁磁性。但是，它的实质性实现仍然难以捉摸。到目前为止，仅通过实验制作了人造李布（Lieb）晶格。在这里，基于第一性原理和紧密结合的计算，我们发现最近合成的二维sp2碳共轭共价-有机骨架（sp2c-COF）代表了利勃样晶格的材料实现。掺杂时观察到的铁磁性来自具有理想电子异质性（EI）的非理想Lieb晶格中的Dirac（价）带，而不是理想Lieb晶格中的拓扑平坦带。EI具有较大的现场能量差，并且在角和边缘中心配体之间具有很强的二聚作用，抑制了通常的弥散狄拉克谱带的动能，使其对自旋极化不稳定。我们预测单层sp2c-COF的自旋密度更高，以适应更高的掺杂浓度并减少层间相互作用。

更新日期：2019-05-17

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