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ナノスケールスピン液体におけるスピノン超流動によるスピン変換理論

Publicly Offered Research

Project Areanano spin conversion science
Project/Area Number 15H01025
Research Category

Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

Allocation TypeSingle-year Grants
Review Section Science and Engineering
Research InstitutionInstitute of Physical and Chemical Research

Principal Investigator

小野田 繁樹  国立研究開発法人理化学研究所, 古崎物性理論研究室, 専任研究員 (70455335)

Project Period (FY) 2015-06-29 – 2017-03-31
Project Status Completed (Fiscal Year 2016)
Budget Amount *help
¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2016: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2015: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Keywordsスピン流 / スピン液体 / スピンアイス / 物性理論 / 磁性 / スピントロニクス / 量子スピン液体 / スピントロにクス
Outline of Annual Research Achievements

U(1)量子スピン液体の候補物質である希土類磁性絶縁体Pr2Zr2O7などは、電荷0・スピン1/2を運ぶ分化したボーズ粒子スピノンを、励起エネルギーギャップを持った準粒子として自発的に生じると考えられている。一方、Yb2Ti2O7は、このU(1)量子スピン液体からHiggs閉じ込め強磁性相に相転移した系として知られている。そこでは、スピノンがボーズ凝縮して超伝導体におけるクーパー対のように振る舞うと考えられるため、超伝導におけるジョセフソン効果の磁気的類似現象の発現が期待される。これらは、散逸のない革新的スピン変換・制御機能の理論的発見に直接つながる、きわめて重要な現象である。我々は、Yb2Ti2O7/Pr2Zr2O7/Yb2Ti2O7、及び、Yb2Ti2O7/Yb2Ti2O7/Yb2Ti2O7の薄膜状ナノ接合系の有効スピン理論模型を解析をした。スピン模型の結合定数、および、左右両側のYb2Ti2O7における強磁性磁化の方向やスピノンの位相差などの境界条件を変化させながら、接合系のスピン構造、スピノン凝縮成分の空間分布と位相分布、接合を流れる局所スピノン流などを計算した。その結果、Yb2Ti2O7/Yb2Ti2O7/Yb2Ti2O7接合系では、左右両側のスピノンの位相差に比例してスピノンのsupercurrentが増大し、接合の厚さによらず内部であまり減衰しないことを示した。Yb2Ti2O7/Pr2Zr2O7/Yb2Ti2O7接合系では、スピノンの位相差について、2π、4π、6π周期のサイン関数を成分にもつスピノン流が発生し、その強度は接合の厚みとともに減衰することを示した。スピノンは磁化のモノポールを運ぶことから、この場合には、縦スピン流と、接合の両側のスピノンの位相差の間に一般化されたジョセフソンの関係式が成立することがわかった。本成果について論文投稿準備中である。

Research Progress Status

28年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

28年度が最終年度であるため、記入しない。

Report

(2 results)
  • 2016 Annual Research Report
  • 2015 Annual Research Report
  • Research Products

    (19 results)

All 2017 2016 2015 Other

All Int'l Joint Research (4 results) Journal Article (3 results) (of which Int'l Joint Research: 2 results,  Peer Reviewed: 3 results,  Acknowledgement Compliant: 3 results) Presentation (10 results) (of which Int'l Joint Research: 7 results,  Invited: 4 results) Remarks (2 results)

  • [Int'l Joint Research] NIST(米国)

    • Related Report
      2016 Annual Research Report
  • [Int'l Joint Research] Institute Laue Langevin(France)

    • Related Report
      2016 Annual Research Report
  • [Int'l Joint Research] NIST/Georgia Regents University(米国)

    • Related Report
      2015 Annual Research Report
  • [Int'l Joint Research] Institute Laue Langevin(France)

    • Related Report
      2015 Annual Research Report
  • [Journal Article] Quadrupole Order in the Frustrated Pyrochlore Tb2+xTi2-xO7+y2016

    • Author(s)
      H. Takatsu, S. Onoda, H. Takatsu, S. Kittaka, A. Kasahara, Y. Kono, T. Sakakibara, Y. Kato, B. Fåk, J. Ollivier, J. W. Lynn, T. Taniguchi, M. Wakita, H. Kadowaki
    • Journal Title

      Physical Review Letters

      Volume: 116 Issue: 21 Pages: 2172011-5

    • DOI

      10.1103/physrevlett.116.217201

    • NAID

      120005848239

    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
  • [Journal Article] Quadrupole Order in the Frustrated Pyrochlore Tb2+xTi2-xO7+y2016

    • Author(s)
      H. Takatsu, S. Onoda, S. Kittaka, A. Kasahara, Y. Kono, T. Sakakibara, Y. Kato, B. Fak, J. Ollivier, J.W. Lynn, T. Taniguchi, M. Wakita, H. Kadowaki
    • Journal Title

      Physical Review Letters

      Volume: 未定

    • NAID

      120005848239

    • Related Report
      2015 Annual Research Report
    • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
  • [Journal Article] Numerical evidence of quantum melting of spin ice: quantum-classical crossover2015

    • Author(s)
      Yasuyuki Kato, Shigeki Onoda
    • Journal Title

      Physical Review Letters

      Volume: 115 Issue: 7 Pages: 077202-077202

    • DOI

      10.1103/physrevlett.115.077202

    • Related Report
      2015 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Presentation] Quantum spin ice under a [111] magnetic field2017

    • Author(s)
      T. A. Boesen, S. Onoda
    • Organizer
      American Physical Society March Meeting 2016
    • Place of Presentation
      New Orleans, USA
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] パイロクロア量子スピンアイス系のスピンダイナミクスの理論2016

    • Author(s)
      小野田繁樹, Trinanjan Datta
    • Organizer
      日本物理学会第71回年次大会
    • Place of Presentation
      東北学院大学、仙台市、宮城県
    • Year and Date
      2016-03-19
    • Related Report
      2015 Annual Research Report
  • [Presentation] Theory for magnetic excitations in quantum spin ice2016

    • Author(s)
      Shigeki Onoda, Trinanjan Datta
    • Organizer
      American Physical Society March Meeting 2016
    • Place of Presentation
      Baltimore, MD, USA
    • Year and Date
      2016-03-15
    • Related Report
      2015 Annual Research Report
  • [Presentation] Quantum spin ice: current issues and beyond2016

    • Author(s)
      Shigeki Onoda
    • Organizer
      2016 Quantum Materials Symposium
    • Place of Presentation
      Muui Island, Korea
    • Year and Date
      2016-02-25
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] Magnetic analogue of superconductivity in the Higgs ferromagnetic phase of quantum spin ice2016

    • Author(s)
      Sho Nakosai, Shigeki Onoda
    • Organizer
      8th International Conference on Highly Frustrated Magnetism
    • Place of Presentation
      Taipei, Taiwan
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Resolving controversies on quantum spin ice: Yb2Ti2O7 and Tb2Ti2O72016

    • Author(s)
      S. Onoda
    • Organizer
      8th International Conference on Highly Frustrated Magnetism
    • Place of Presentation
      Taipei, Taiwan
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Quantum spin ice under a [111] magnetic field2016

    • Author(s)
      S. Onoda
    • Organizer
      Frustrated Magnetism Workshop
    • Place of Presentation
      Chennai, India
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] パイロクロアU(1)量子スピン液体・秩序相における励起:フォトン、量子スピンアイスモノポール、ヒッグスモード2015

    • Author(s)
      小野田繁樹
    • Organizer
      物性研短期研究会「スピン系物理の深化と最前線」
    • Place of Presentation
      東京大学物性研究所、柏市、千葉県
    • Year and Date
      2015-11-17
    • Related Report
      2015 Annual Research Report
    • Invited
  • [Presentation] Theory for electronic properties of oxide pyrochlores: quantum spin ice and iridates2015

    • Author(s)
      Shigeki Onoda
    • Organizer
      TMU International Symposium on “New Quantum Phases Emerging from Novel Crystal Structure”
    • Place of Presentation
      首都大学東京、八王子市、東京都
    • Year and Date
      2015-09-25
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] Thermal, transport, and spectral properties of generic quantum spin ice beyond the mean-field theory2015

    • Author(s)
      Shigeki Onoda
    • Organizer
      The 20th International Conference on Magnetism
    • Place of Presentation
      Barcelona, Spain
    • Year and Date
      2015-07-06
    • Related Report
      2015 Annual Research Report
    • Int'l Joint Research
  • [Remarks] Melting of frozen frustration

    • URL

      http://www.riken.jp/en/research/rikenresearch/highlights/8138/

    • Related Report
      2015 Annual Research Report
  • [Remarks] プレスリリース「凍ったスピンをさらに冷やして量子効果で液体に融かす」

    • URL

      http://www.riken.jp/pr/press/2015/20150821_2/

    • Related Report
      2015 Annual Research Report

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Published: 2015-07-02   Modified: 2022-01-28  

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