Realization of Lieb lattice in covalent-organic frameworks with tunable topology and magnetism
Bin Cui, Xingwen Zheng, Jianfeng Wang, Desheng Liu, Shijie Xie, Bing Huang
Abstract
Abstract 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., sp 2 C-COF and sp 2 N-COF, are actually the first two material realizations of organic-ligand-based Lieb lattice. Interestingly, the sp 2 C-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.