Abstract
Rutile (R) phase VO2 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 (M1) phase below TMIT∼340K. It has been experimentally shown that one can control this transition by doping VO2. In particular, doping with oxygen vacancies (VO) 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 VO2, 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 M1 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 VO's tend to change the V-3d filling away from its nominal half-filled value, with the egπ orbitals competing with the otherwise dominant a1g orbital. Loss of this near orbital polarization of the a1g 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.
| Original language | English |
|---|---|
| Article number | 155129 |
| Journal | Physical Review B |
| Volume | 101 |
| Issue number | 15 |
| DOIs | |
| State | Published - Apr 15 2020 |
Funding
This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan . Work at Oak Ridge National Laboratory and Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, as part of the Computational Materials Sciences Program and Center for Predictive Simulation of Functional Materials. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. F.L. acknowledges financial support from the DFG project LE 2446/4-1. DFT+DMFT computations were performed at the JURECA Cluster of the Jülich Supercomputing Centre (JSC) under project number hhh08. Work at Oak Ridge National Laboratory and Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, as part of the Computational Materials Sciences Program and Center for Predictive Simulation of Functional Materials. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. F.L. acknowledges financial support from the DFG project LE 2446/4-1. DFT+DMFT computations were performed at the JURECA Cluster of the Julich Supercomputing Centre (JSC) under project number hhh08.
| Funders | Funder number |
|---|---|
| DOE Office of Science | |
| Julich Supercomputing Centre | hhh08 |
| U.S. Department of Energy | |
| Office of Science | DE-AC02-05CH11231 |
| Basic Energy Sciences | |
| Argonne National Laboratory | |
| Oak Ridge National Laboratory | |
| Division of Materials Sciences and Engineering | DE-AC05-00OR22725 |
| Deutsche Forschungsgemeinschaft | LE 2446/4-1 |