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Metallization of vanadium dioxide driven by large phonon entropy

机译：大声子熵驱动的二氧化钒金属化

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摘要

二氧化钒会发生从一个高温金属相到一个低温绝缘相的转变，同时伴随着晶格结构的一个变化。但是尽管进行了多年研究，这种耦合在一起的结构和电子转变的起源仍然不清楚。现在，John Budai及同事发现，某一类别的晶格振动(强非谐声子）在驱动这两个相互竞争的相之间的转变中起关键作用。关于这一种以及其他相关过渡金属氧化物的行为的一个更为全面的物理模型，应能帮助光电子和自旋电子等领域的新型功能材料的设计和开发。%Phase competition underlies many remarkable and technologically important phenomena in transition metal oxides. Vanadium dioxide (VO_2) exhibits a first-order metal-insulator transition (MIT) near room temperature, where conductivity is suppressed and the lattice changes from tetragonal to monoclinic on cooling. Ongoing attempts to explain this coupled structural and electronic transition begin with two alternative starting points: a Peierls MIT driven by instabilities in electron-lattice dynamics and a Mott MIT where strong electron-electron correlations drive charge localization. A key missing piece of the VO_2 puzzle is the role of lattice vibrations. Moreover, a comprehensive thermodynamic treatment must integrate both entropic and energetic aspects of the transition. Here we report that the entropy driving the MIT in VO_2 is dominated by strongly anharmonic phonons rather than electronic contributions, and provide a direct determination of phonon dispersions. Our ab initio calculations identify softer bonding in the tetragonal phase, relative to the monodinic phase, as the origin of the large vibrational entropy stabilizing the metallic rutile phase. They further reveal how a balance between higher entropy in the metal and orbital-driven lower energy in the insulator fully describes the thermodynamic forces controlling the MIT. Our study illustrates the critical role of anharmonic lattice dynamics in metal oxide phase competition, and provides guidance for the predictive design of new materials.
机译：二氧化钒会发生从一个高温金属相到一个低温绝缘相的转变，同时伴随着晶格结构的一个变化。但是尽管进行了多年研究，这种耦合在一起的结构和电子转变的起源仍然不清楚。现在，John Budai及同事发现，某一类别的晶格振动(强非谐声子）在驱动这两个相互竞争的相之间的转变中起关键作用。关于这一种以及其他相关过渡金属氧化物的行为的一个更为全面的物理模型，应能帮助光电子和自旋电子等领域的新型功能材料的设计和开发。%Phase competition underlies many remarkable and technologically important phenomena in transition metal oxides. Vanadium dioxide (VO_2) exhibits a first-order metal-insulator transition (MIT) near room temperature, where conductivity is suppressed and the lattice changes from tetragonal to monoclinic on cooling. Ongoing attempts to explain this coupled structural and electronic transition begin with two alternative starting points: a Peierls MIT driven by instabilities in electron-lattice dynamics and a Mott MIT where strong electron-electron correlations drive charge localization. A key missing piece of the VO_2 puzzle is the role of lattice vibrations. Moreover, a comprehensive thermodynamic treatment must integrate both entropic and energetic aspects of the transition. Here we report that the entropy driving the MIT in VO_2 is dominated by strongly anharmonic phonons rather than electronic contributions, and provide a direct determination of phonon dispersions. Our ab initio calculations identify softer bonding in the tetragonal phase, relative to the monodinic phase, as the origin of the large vibrational entropy stabilizing the metallic rutile phase. They further reveal how a balance between higher entropy in the metal and orbital-driven lower energy in the insulator fully describes the thermodynamic forces controlling the MIT. Our study illustrates the critical role of anharmonic lattice dynamics in metal oxide phase competition, and provides guidance for the predictive design of new materials.

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  • 来源
    《Nature》 |2014年第7528期|535-539B1|共6页
  • 作者

    John D. Budai; Jiawang Hong; Michael E. Manley; Eliot D. Specht; Chen W. Li; Jonathan Z. Tischler; Douglas L. Abernathy; Ayman H. Said; Bogdan M. Leu; Lynn A. Boatner; Robert J. McQueeney; Olivier Delaire;

  • 作者单位

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA;

    Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA;

    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA;

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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