title: Orbital-assisted metal-insulator transition in VO2.
abstract: We found direct experimental evidence for an orbital switching in the V 3d states across the metal-insulator transition in VO2. We have used soft-x-ray absorption spectroscopy at the V L2,3 edges as a sensitive local probe and have determined quantitatively the orbital polarizations. These results strongly suggest that, in going from the metallic to the insulating state, the orbital occupation changes in a manner that charge fluctuations and effective bandwidths are reduced, that the system becomes more one dimensional and more susceptible to a Peierls-like transition, and that the required massive orbital switching can only be made if the system is close to a Mott insulating regime.
authors.affiliation: II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany.
authors.forename: M W
authors.initials: MW
authors.lastname: Haverkort
authors.forename: Z
authors.initials: Z
authors.lastname: Hu
authors.forename: A
authors.initials: A
authors.lastname: Tanaka
authors.forename: W
authors.initials: W
authors.lastname: Reichelt
authors.forename: S V
authors.initials: SV
authors.lastname: Streltsov
authors.forename: M A
authors.initials: MA
authors.lastname: Korotin
authors.forename: V I
authors.initials: VI
authors.lastname: Anisimov
authors.forename: H H
authors.initials: HH
authors.lastname: Hsieh
authors.forename: H-J
authors.initials: HJ
authors.lastname: Lin
authors.forename: C T
authors.initials: CT
authors.lastname: Chen
authors.forename: D I
authors.initials: DI
authors.lastname: Khomskii
authors.forename: L H
authors.initials: LH
authors.lastname: Tjeng