Compton profile of ${\mathrm{VO}}_{2}$ across the metal-insulator transition: Evidence of a non-Fermi liquid metal

Compton profile of ${VO}_{2}$ across the metal-insulator transition: Evidence of a non-Fermi liquid metal

Ilkka Kylänpää, Ye Luo, Olle Heinonen, Paul R. C. Kent, and Jaron T. Krogel

Phys. Rev. B 99, 075154 – Published 26 February 2019

Abstract

Many-body diffusion Monte Carlo is used to obtain the first-principles momentum distribution and Compton profile of vanadium dioxide. Our results for the Compton profile are in good agreement with the experimental values, and we show that good qualitative agreement in the scaled Compton profile difference across the monoclinic to rutile phase transition depends on an accurate description of electron correlation. The electron momentum distribution enables new insights into the metal-insulator phase transition. For example, the probability for electron scattering in the proximity of the Fermi surface (forward scattering) is suppressed in the vanadium chain direction (rutile $c$ axis) but enhanced in perpendicular directions. However, along the $c$ axis we observe an increase at $\sim 2 k_{F}$ in the momentum distribution, which is characteristic for Friedel oscillations (backscattering). Our analysis of the momentum distribution supports experimentally observed anisotropies and provides an explanation for the anomalously low electronic thermal conductivity observed recently in the metallic phase [S. Lee et al., Science 355, 371 (2017)]. Moreover, our results indicate non-Fermi liquid behavior as well as quasi-one-dimensional Friedel oscillations in the metallic rutile phase, which is reminiscent of a Tomanaga-Luttinger liquid with impurities.

Received 18 May 2018

DOI:https://doi.org/10.1103/PhysRevB.99.075154

Physics Subject Headings (PhySH)

Fermi surface Phase transitions

Functional materials

Compton scattering Diffusion quantum Monte Carlo

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ilkka Kylänpää^1,2,*, Ye Luo³, Olle Heinonen^4,5, Paul R. C. Kent^6,7, and Jaron T. Krogel¹

¹Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
²Computational Physics Laboratory, Tampere University, P.O. Box 692, 33014 Tampere, Finland
³Computational Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
⁴Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
⁵Center for Hierarchical Material Design, Northwestern-Argonne Institute for Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
⁶Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
⁷Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

^*ilkka.kylanpaa@tuni.fi

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Vol. 99, Iss. 7 — 15 February 2019

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Figure 1
Finite-size effects on the momentum distribution considered as the difference between 72-atom and 48-atom as well as 96-atom and 48-atom supercells.
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Figure 2
Scaled Compton profile difference across the phase transition. Experimental data [26] in green have been multiplied by 5 in order to account for the quantitative difference in the scaled difference profile. Quantum Monte Carlo with $1 σ$ statistical error is shown in blue (on top of the experiment), and DFT from this work (LDA+ $U$ with a DMC-optimized $U$ value, $U = 3.5$ eV) is shown as a black dashed line. Here we concentrate on the region in which DFT, QMC, and the experiments have noticeable differences, i.e., the region of valence electron contributions.
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Figure 3
Supercell crystal structures of $R$ and $M 1$ phases specifying directions used in the analysis. The vanadium chain direction (rutile $c$ axis in general) is out of plane. Subtle structural changes can be seen, e.g., the misalignment of the V atoms along the chain direction (zigzag “chain”). On the right we show the momentum distribution in the $R$ phase along the vanadium chain direction. The statistical error bars are smaller than the linewidth. Vertical lines are estimates for the Fermi momentum $k_{F}$ and $2 k_{F}$ obtained from the angular-averaged “isotropic” momentum distribution.
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Figure 4
Anisotropies of the momentum distribution on two different planes. Plane 1: V chain direction ( $y$ axis) versus V-O direction ( $x$ axis) for (a) the $R$ phase and (b) $M 1$ phase. Plane 2: V chain direction ( $y$ axis) versus V-V direction ( $x$ axis) for (c) the $R$ phase and (d) $M 1$ phase. The smaller circle is an estimate of Fermi momentum $k_{F}$ from the angular-averaged “isotropic” momentum distribution, and the larger circle is at $\sim 2 k_{F}$ .
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Figure 5
Difference in the momentum distribution across the phase transition on the same two planes as in Fig. 4: (a) V chain direction ( $y$ axis) versus V-O direction ( $x$ axis) and (b) V chain direction ( $y$ axis) versus V-V direction ( $x$ axis). The smaller circle is an estimate of Fermi momentum $k_{F}$ from the angular-averaged isotropic momentum distribution, and the larger circle is at $\sim 2 k_{F}$ . In (c) the differences are given in four different directions and also for the angular-averaged momentum distributions. In (c) the V-V 1 direction corresponds to the $x$ axis of (b), and V-V 2 is the direction straight up in Fig. 3, i.e., perpendicular to V-V 1.
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Figure 6
Electron density isosurfaces (atomic units, $e / a_{0}^{3}$ ): (a) $R$ phase with an isovalue of 0.06, (b) $R$ phase with an isovalue of 0.08, (c) $M 1$ phase with an isovalue of 0.06, and (d) $M 1$ phase with an isovalue of 0.08. Quantum Monte Carlo electron densities are from the Materials Data Facility related to Ref. [8]. For clarity the atoms are not shown in (b) and (d). These figures were made with xcrysden [87, 88].
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Physical Review B

covering condensed matter and materials physics

Compton profile of ${VO}_{2}$ across the metal-insulator transition: Evidence of a non-Fermi liquid metal

Ilkka Kylänpää, Ye Luo, Olle Heinonen, Paul R. C. Kent, and Jaron T. Krogel

Phys. Rev. B 99, 075154 – Published 26 February 2019

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Physical Review B

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Compton profile of VO2 across the metal-insulator transition: Evidence of a non-Fermi liquid metal

Ilkka Kylänpää, Ye Luo, Olle Heinonen, Paul R. C. Kent, and Jaron T. Krogel

Phys. Rev. B 99, 075154 – Published 26 February 2019

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Compton profile of ${VO}_{2}$ across the metal-insulator transition: Evidence of a non-Fermi liquid metal