DFT insights into flat bands of Kagome FeSn materials*

Kagome FeSn materials have attracted significant attention for their potential applications in low-energy electronics, spintronics, and other potential technologies.^[1,2] These properties stem from a narrow nearly dispersionless band near the Fermi level, known as flat bands.^[3] This flat band can form the basis of novel correlated electron states, enabling possible superconductivity.^[4] Despite concentrated efforts on understanding flat bands in kagome FeSn materials, the precise correlation between these flat band structures and the magnetic behaviors of these materials requires further investigation.

In this study, we used density functional theory (DFT) calculations to comprehensively investigate the flat bands of kagome FeSn within antiferromagnetic, ferromagnetic, and nonmagnetic spin configurations. Analysis of the projected density of states, wave function, and projected band characters demonstrates that flat band locations, as well as whether they can be observed or not, vary across different magnetic configurations, suggesting a role played by magnetic symmetry in their formation. However, the primary d-orbital contribution to the flat band is independent of magnetic behavior.