Using photoelectron momentum microscopy, we have mapped the complete two-dimensional band structure of the van der Waals crystal NbOCl₂. Our measurements reveal an almost perfectly flat band that spans the entire momentum space and is well separated from all other, dispersive bands. This uniquely isolated flat band establishes NbOCl₂ as an ideal platform for investigating correlation-driven phenomena, as well as for exploring the role of dispersionless quasiparticles in lightwave electronics and light-induced band engineering.

The results have been obtained in in close collaboration with the group of Ulrich Höfer (Philipps-University Marburg, University of Regensburg) and have been published in Communications Materials (external link, opens in a new window).