Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
2012-02-07
Physics
Condensed Matter
Strongly Correlated Electrons
Scientific paper
Vanadium dioxide undergoes a first order metal-insulator transition (MIT) at 340 K. At high temperature, the crystal structure is metallic with the rutile structure (R), while it transforms to the monoclinic (M$_1$) phase and becomes insulating below the transition temperature. Experimental evidence suggests that the insulator is obtained due to strong correlations in this material, however density functional theory (DFT) predicts the M$_1$ phase to be metallic. In this work, we develop and carry out state of the art linear scaling DFT calculations refined with non-local dynamical mean-field theory (DMFT). We validate our approach by applying this cutting edge methodology to the M$_1$ phase of VO$_2$. We find that a Peierls-Mott instability is responsible for the insulating M$_1$ phase, which furthermore survives a large degree of disorder accounting for the MIT observed when no long-range crystallographic order is present. The Peierls-Mott instability involves two electrons per vanadium atom in $t_{2g}$ orbitals and reconciles the Peierls picture with recent soft x-ray absorption spectroscopy (XAS), which points towards a breaking of the one electron per 3d orbital picture suggested early by Goodenough. Finally, since fluctuations in VO$_2$ thin film deposition may cause departure from the ideal stoichiometry, we discuss how the MIT is affected by oxygen vacancies.
Hine Nicholas D. M.
Kotliar Gabriel
Littlewood Peter B.
O'Regan David D.
Payne Mike C.
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