Spectroscopy of metallic and insulatingV2O3

Abstract

${\mathrm{V}}_2{\mathrm{O}}_3$ exhibits as a function of temperature a metal-insulator transition (MIT) associated with a structural and a magnetic transition, which we have studied with x-ray-absorption measurements of ${\mathrm{V}}_2{\mathrm{O}}_3$ at the V $2p$ and O $1s$ edge as well as photoemission measurements above and below the MIT. The O $1s$ edge shifts $\sim 0.3\mathrm{eV}$ to lower energy in the metallic phase and the linear dichroism is enhanced in the insulating state, an enhancement discussed in a molecular-orbital picture. These effects are independent of whether the insulating state is achieved by cooling, Cr doping, or stress. We conclude the monoclinic distortion plays only a minor role in the MIT; the major factor is the change in the $c/a$ ratio. The V $2p$ edge is much narrower in the insulating phase, perhaps due to changes in electron phonon coupling.