Fig. 1: NbOCl2 as a potential host of flat bands.
From: Observation of an isolated flat band in the van der Waals crystal NbOCl2
a, b Crystal structure of the van der Waals crystal NbOCl2 from side and top views. c The surface Brillouin zone with labeled high-symmetry points. d, e Ideal square lattice of Nb atoms without Peierls distortion (d). The green shadows represent the Nb 4\({d}_{z}^{2}\) orbitals, whose overlap results in a partially flat band as schematically shown in (e). f, g Realistic rectangular lattice of Nb atoms with a Peierls distortion (f) and corresponding ideal flat band as schematically shown in (g) owing to the band folding and gap opening. The dashed curves are dispersions without gap opening.
