Correlation Assisted Phonon Softening and the Orbital-selective Peierls Transition in VO2

Abstract

To explore the driving mechanisms of the metal-insulator transition (MIT) and the structural transition in VO2, we have investigated phonon dispersions of rutile VO2 (R-VO2) in the density functional theory (DFT) and the DFT+U (U: Coulomb correlation) band calculations. We have found that the phonon softening instabilities occur in both cases, but the softened phonon mode only in the DFT+U describes properly both the MIT and the structural transition from R-VO2 to monoclinic VO2 (M-1-VO2). The present ab initio phonon dispersion calculations clearly demonstrate that the Coulomb correlation effect plays an essential role of assisting the Peierls transition in R-VO2 and producing the spin-Peierls ground state in M-1-VO2.