Transfer of Spectral Weight and Symmetry across the Metal-Insulator Transition inVO2

Abstract

We present a detailed study of the valence and conduction bands of ${\mathrm{VO}}_2$ across the metal-insulator transition using bulk-sensitive photoelectron and O $K$ x-ray absorption spectroscopies. We observe a giant transfer of spectral weight with distinct features that require an explanation which goes beyond the Peierls transition model as well as the standard single-band Hubbard model. Analysis of the symmetry and energies of the bands reveals the decisive role of the V $3d$ orbital degrees of freedom. Comparison to recent realistic many body calculations shows that much of the $k$ dependence of the self-energy correction can be cast within a dimer model.