Emergence of nearly flat bands through a kagome lattice embedded in an epitaxial two-dimensional Ge layer with a bitriangular structure

Ge atoms segregating on zirconium diboride thin films grown on Ge(111) were found to crystallize into a two-dimensional bitriangular structure, which was recently predicted to be a flat band material through an embedded kagome lattice. Angle-resolved photoelectron emission experiments together with theoretical calculations pointed out the existence of a nearly flat band in spite of non-negligible in-plane long-range hopping and interactions with the substrate. This provides an experimental verification for the fact that a flat band can emerge from the electronic coupling between atoms and not from the geometry of the atomic structure.