General construction of flat bands with and without band crossings based on wave function singularity
General construction of flat bands with and without band crossings based on wave function singularity
In this work, we develop a systematic method of constructing flat-band models with and without band crossings. Our construction scheme utilizes the symmetry and spatial shape of a compact localized state (CLS) and also the singularity of the flat-band wave function obtained by a Fourier transform of the CLS (FT-CLS). …