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Doping a bad metal: Origin of suppression of the metal-insulator transition in nonstoichiometric VO2
- Source :
- Physical Review B. 101
- Publication Year :
- 2020
- Publisher :
- American Physical Society (APS), 2020.
-
Abstract
- Rutile ($R$) phase ${\mathrm{VO}}_{2}$ is a quintessential example of a strongly correlated bad metal, which undergoes a metal-insulator transition (MIT) concomitant with a structural transition to a V-V dimerized monoclinic (${M}_{1}$) phase below ${T}_{\text{MIT}}\ensuremath{\sim}340\phantom{\rule{0.28em}{0ex}}\text{K}$. It has been experimentally shown that one can control this transition by doping ${\mathrm{VO}}_{2}$. In particular, doping with oxygen vacancies (${V}_{\text{O}}$) has been shown to completely suppress this MIT without any structural transition. We explain this suppression by elucidating the influence of oxygen vacancies on the electronic structure of the metallic $R$ phase ${\mathrm{VO}}_{2}$, explicitly treating strong electron-electron correlations using dynamical mean-field theory (DMFT) as well as diffusion Monte Carlo (DMC) flavor of quantum Monte Carlo (QMC) techniques. DMC calculations show a gap closure in the ${M}_{1}$ phase when vacancies are present, suggesting that when vacancies are introduced in the high-temperature rutile phase, the dimerized insulating phase cannot be reached when temperature is lowered. Both DMFT and DMC calculations of nonstoichiometric metallic rutile phase shows that this tendency not to dimerize in the presence of vacancies is because ${V}_{\text{O}}$'s tend to change the $\mathrm{V}\text{\ensuremath{-}}3d$ filling away from its nominal half-filled value, with the ${e}_{g}^{\ensuremath{\pi}}$ orbitals competing with the otherwise dominant ${a}_{1g}$ orbital. Loss of this near orbital polarization of the ${a}_{1g}$ orbital is associated with a weakening of electron correlations, especially along the V-V dimerization direction. This removes a charge-density wave (CDW) instability along this direction above a critical doping concentration, which further suppresses the metal-insulator transition. Our study also suggests that the MIT is predominantly driven by a correlation-induced CDW instability along the V-V dimerization direction.
- Subjects :
- Quantum Monte Carlo
FOS: Physical sciences
02 engineering and technology
Electron
Electronic structure
114 Physical sciences
01 natural sciences
Condensed Matter::Materials Science
Condensed Matter - Strongly Correlated Electrons
Atomic orbital
Phase (matter)
0103 physical sciences
Physics::Atomic and Molecular Clusters
Metal–insulator transition
010306 general physics
Physics
Condensed Matter - Materials Science
Strongly Correlated Electrons (cond-mat.str-el)
Condensed matter physics
Materials Science (cond-mat.mtrl-sci)
021001 nanoscience & nanotechnology
216 Materials engineering
Condensed Matter::Strongly Correlated Electrons
Diffusion Monte Carlo
0210 nano-technology
Monoclinic crystal system
Subjects
Details
- ISSN :
- 24699969 and 24699950
- Volume :
- 101
- Database :
- OpenAIRE
- Journal :
- Physical Review B
- Accession number :
- edsair.doi.dedup.....33ed7a725ae708800c9f10cba85fb5fe
- Full Text :
- https://doi.org/10.1103/physrevb.101.155129