Coulomb correlations and orbital polarization in the metal-insulator transition ofVO2

The quasiparticle spectra in the metallic rutile and insulating monoclinic phases of $\mathrm{V}{\mathrm{O}}_2$ are shown to be dominated by local Coulomb interactions. In the rutile phase the small orbital polarization among V $3d$ $t_{2g}$ states leads to weak static but strong dynamical correlations. In the monoclinic phase the large $3d$ orbital polarization caused by the $\mathrm{V}\mathrm{V}$ Peierls distortion gives rise to strong static correlations which are shown to be the primary cause of the insulating behavior.