Visualizing the electronic structure of kagome magnet LuMn₆Sn₆ by angle-resolved photoemission spectroscopy

Abstract Searching for the dispersionless flat band (FB) in quantum materials, especially in topological systems, becomes an interesting topic. The kagome lattice is an ideal platform for such exploration because the FB can be naturally induced by the underlying destructive interference. Nevertheless, the magnetic kagome system that hosts the FB close to the Fermi level ( E F ) is exceptionally rare. Here, we study the electronic structure of a kagome magnet LuMn 6 Sn 6 by combining angle-resolved photoemission spectroscopy and density functional theory calculations. The observed Fermi-surface topology and overall band dispersions are similar to previous studies of the X Mn 6 Sn 6 ( X = Dy, Tb, Gd, Y) family of compounds. We clearly observe two kagome-derived FBs extending through the entire Brillouin zone, and one of them is located just below E F . The photon-energy-dependent measurements reveal that these FBs are nearly dispersionless along the k z direction as well, supporting the quasi-two-dimensional character of such FBs. Our results complement the X Mn 6 Sn 6 family and demonstrate the robustness of the FB features across this family.