Abstract
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. Angle-resolved photoemission experiments together with theoretical calculations verified the existence of a nearly flat band in spite of non-negligible in-plane long-range hopping and interactions with the substrate. This provides the first experimental evidence that a flat band can emerge from the electronic coupling between atoms and not from the geometry of the atomic structure.
Highlights
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
A nearly flat band and long-range ferromagnetic order have been reported for the layered, quasi-2D Fe3Sn2 crystal consisting of Fe kagome lattices [9]
Summary
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. Flat bands can emerge as solution of the Schrödinger equation for Bloch tightbinding Hamiltonians of particular geometrically frustrated two-dimensional (2D) structures such as Lieb, checkerboard, dice or kagome lattices [13–15] Such 2D lattices remain rare in their free-standing forms, and are mostly observed within the crystal or at the surface of layered materials [9,16–18]. For a particular relation between the difference of site energies and the hopping integral coefficients, one of the eigensolutions of the tight-binding Hamiltonian is a flat band [24] In this Rapid Communication, we demonstrate that Ge atoms crystallize spontaneously into such a bitriangular lattice on Zr-terminated zirconium diboride (ZrB2) thin films grown on Ge(111) substrates.
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