Fig. 4: Anisotropic optical gap.
From: Observation of an isolated flat band in the van der Waals crystal NbOCl2
a, b Optical extinction spectrum for light polarized along the b-axis (a) and the c-axis (b). c Optical extinction map as a function of light polarization and photon energy. The corresponding crystal orientations are labeled. d Schematic band structure with experimentally determined bottom of CB, flat band, and band edge of the remote VBs. The observed optical gap is indicated by the red arrow.
