Cooperative Effects of Strain and Electron Correlation in Epitaxial VO2 and NbO2

Abstract

We investigate the electronic structure of the epitaxial VO${}_2$ films in the rutile phase using the density functional theory combined with the slave spin method (DFT+SS). In DFT-SS, the multiorbital Hubbard interactions are added to a DFT-fit tight-binding model, and we employ the slave-spin method to treat the electron correlation. We find that while stretching the system along the rutile $c$-axis results in a band structure favoring an anisotropic orbital fillings, the electron correlation favors an equal electron filling among $t_{2g}$ orbitals. These two distinct effects cooperatively induce interesting orbital-dependent redistributions of the electron occupations and the spectral weights, which pushes the strained VO${}_2$ toward an orbital selective Mott transition (OSMT). The simulated single-particle spectral functions are directly compared to V L-edge resonant X-ray photoemission spectroscopy of epitaxial 10 nm VO${}_2$/TiO${}_2$ (001) and (100) strain orientations. Excellent agreement is observed between the simulations and experimental data regarding the strain-induced evolution of the lower Hubbard band. Simulations of rutile NbO${}_2$ under similar strain conditions as VO${}_2$ are performed, and we predict that OSMT will not occur in rutile NbO${}_2$. Our results indicates that the electron correlation in VO${}_2$ is important and can be modulated even in the rutile phase before the Peierls instability sets in.

arXiv comment8 pages, 9 figures, invited paper for Special Topic: Strain Engineering in Functional Materials by Journal of Applied Physics

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Cited by in corpus (5)

• Unraveling the role of V-V dimer on the vibrational properties of VO${}_2$ by first-principles simulations and Raman spectroscopic analysis
• Correlation induced emergent charge order in metallic vanadium dioxide
• Mechanism of the Resistivity Switching Induced by the Joule Heating in Crystalline NbO${}_2$
• Electronic phase diagram of Cr-doped VO2 epitaxial films studied by in situ photoemission spectroscopy
• Role of surface termination in the metal-insulator transition of V${}_2$O${}_3$(0001) ultrathin films