A Lieb-like lattice in a covalent-organic framework and its Stoner ferromagnetism.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31101812.
- Also identified by DOI 10.1038/s41467-019-10094-3 and PMC identifier 6525167.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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 sp<sup>2</sup> carbon-conjugated covalent-organic framework (sp<sup>2</sup>c-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 sp<sup>2</sup>c-COF to accommodate a higher doping concentration with reduced interlayer interaction.