New Method for Absolute Band Structure Determination by Combining Photoemission with Very-Low-Energy Electron Diffraction: Application to LayeredVSe2

Abstract

We have combined photoelectron spectroscopy (PES) and very-low-energy electron diffraction (VLEED) to study the electronic band structure $E\left(\mathbf{k}\right)$ of a material with complicated unoccupied upper bands, which are incompatible with the free-electron approximation. Using VLEED, we have experimentally determined these bands, and accordingly optimized the PES experiment. PES band mapping using the VLEED upper bands enabled the first consistent resolution of the lower occupied bands, in particular, the perpendicular dispersion $E\left(k_{\perp }\right)$, for a layered material. The combination of PES and VLEED is a powerful method to resolve even very complicated $E\left(\mathbf{k}\right)$ absolutely.