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Thermodynamic investigation into low temperature electronic state of organic superconductors

Research Project

Project/Area Number 17J00096
Research Category

Grant-in-Aid for JSPS Fellows

Allocation TypeSingle-year Grants
Section国内
Research Field Physical chemistry
Research InstitutionOsaka University

Principal Investigator

今城 周作  大阪大学, 理学研究科, 特別研究員(DC2)

Project Period (FY) 2017-04-26 – 2019-03-31
Project Status Completed (Fiscal Year 2017)
Budget Amount *help
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2017: ¥900,000 (Direct Cost: ¥900,000)
Keywords超伝導 / 熱測定 / 有機導体
Outline of Annual Research Achievements

本研究課題では有機超伝導体の低温電子状態を議論するために熱測定を主体とした物性測定への装置開発、および測定を行った。装置の開発という点においては、いくつかの改良によって微小試料用角度分解熱量計という、100マイクログラム程度の微小単結晶でも断熱空間で熱容量の磁場角度依存性を測定できる装置を開発することに成功した。他にも熱電効果の測定装置開発なども行なった。
測定では①dimer-Mott系②non-dimerized系と呼ばれる有機超伝導体を中心に研究を行った。①のdimer-Mott系は有機分子が二量体を作ることで半充填バンドを作っていると見做せる系であり、電子相関が強い場合はそのdimerにスピン1/2が局在したMott絶縁体となることが知られている。本研究では、そのMott絶縁相に相図上で隣接した超伝導の測定を行った。熱容量から線形の低エネルギー励起構造や波数空間上で四回周期をもった対称性が検出され、この系の超伝導がd波超伝導であることを明らかにした。また、その対称性の位相が格子形状に影響されて変化することを発見し、理論研究との整合性からこの系の超伝導が反強磁性スピンのゆらぎによって発現していることがわかった。
②のnon-dimerized系では①の系と異なり、二量化がないために1/4充填バンドを形成すると知られている。このような系ではスピンの自由度がなく、電荷の自由度が重要と考えられている。この系の超伝導の測定を行なったところ、①とは異なり、低エネルギー励起構造が抑制される振舞いが見られた。一方で四回周期をもつことから異方的であることはわかり、これらの結果から拡張s波という状態が成り立っている可能性が示唆された。この対称性は電荷ゆらぎを媒介にした超伝導がもつ可能性が理論的に予想されており、この系の超伝導が電荷の自由度に起因していることがわかった。

Research Progress Status

翌年度、交付申請を辞退するため、記入しない。

Strategy for Future Research Activity

翌年度、交付申請を辞退するため、記入しない。

Report

(1 results)
  • 2017 Annual Research Report
  • Research Products

    (18 results)

All 2018 2017 Other

All Int'l Joint Research (1 results) Journal Article (7 results) (of which Int'l Joint Research: 3 results,  Peer Reviewed: 7 results,  Open Access: 2 results) Presentation (8 results) (of which Int'l Joint Research: 6 results) Funded Workshop (2 results)

  • [Int'l Joint Research] School of Science and Technology/Nottingham Trent University(英国)

    • Related Report
      2017 Annual Research Report
  • [Journal Article] Thermodynamic Picture of Dimer-Mott Organic Superconductors Revealed by Heat Capacity Measurements with External and Chemical Pressure Control2018

    • Author(s)
      Nakazawa Yasuhiro、Imajo Shusaku、Matsumura Yuki、Yamashita Satoshi、Akutsu Hiroki
    • Journal Title

      Crystals

      Volume: 8 Issue: 4 Pages: 143-143

    • DOI

      10.3390/cryst8040143

    • Related Report
      2017 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] Thermodynamic Investigation by Heat Capacity Measurements of k-type Dimer-Mott Organic Compounds with Chemical Pressure Tuning2018

    • Author(s)
      Yuki Matsumura, Shusaku Imajo, Satoshi Yamashita, Hiroki Akutsu and Yasuhiro Nakazawa
    • Journal Title

      International Journal of Modern Physics B

      Volume: 32 Issue: 17 Pages: 18400241-7

    • DOI

      10.1142/s0217979218400246

    • Related Report
      2017 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] Development of Light Irradiation Calorimetry System for Molecule-based Compounds2018

    • Author(s)
      Y. Matsumura, S. Kataoka, S. Imajo, S. Yamashita, H. Akutsu, Y. Nakazawa
    • Journal Title

      International Journal of Modern Physics B

      Volume: 32 Issue: 17 Pages: 1840035-1840035

    • DOI

      10.1142/s0217979218400350

    • Related Report
      2017 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Ambient-pressure molecular superconductor with a superlattice containing layers of tris(oxalato)rhodate enantiomers and 18-crown-62017

    • Author(s)
      Martin Lee、Morritt Alexander L.、Lopez Jordan R.、Akutsu Hiroki、Nakazawa Yasuhiro、Imajo Shusaku、Ihara Yoshihiko
    • Journal Title

      Inorganic Chemistry

      Volume: 56 Issue: 2 Pages: 717-720

    • DOI

      10.1021/acs.inorgchem.6b02708

    • Related Report
      2017 Annual Research Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] AC Calorimetry System Using Commercially available Microchip Device and its Application for Tiny Single Crystals of Molecule-Based Compounds2017

    • Author(s)
      M. Murase, S. Yamashita, R. Yoshimoto, S. Imajo, Y. Nakazawa, K. Ueda, and R. Kato
    • Journal Title

      Thermochimica acta

      Volume: 650 Pages: 134-138

    • DOI

      10.1016/j.tca.2016.03.005

    • Related Report
      2017 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Molecular conductors from bis(ethylenedithio)tetrathiafulvalene with tris(oxalato)rhodate2017

    • Author(s)
      Martin Lee、Morritt Alexander L.、Lopez Jordan R.、Nakazawa Yasuhiro、Akutsu Hiroki、Imajo Shusaku、Ihara Yoshihiko、Zhang Bin、Zhang Yan、Guo Yanjun
    • Journal Title

      Dalton Transactions

      Volume: 46 Issue: 29 Pages: 9542-9548

    • DOI

      10.1039/c7dt00881c

    • Related Report
      2017 Annual Research Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Bulk Kosterlitz?Thouless Type Molecular Superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]・18-crown-62017

    • Author(s)
      Martin Lee、Lopez Jordan R.、Akutsu Hiroki、Nakazawa Yasuhiro、Imajo Shusaku
    • Journal Title

      Inorganic Chemistry

      Volume: 56 Issue: 22 Pages: 14045-14052

    • DOI

      10.1021/acs.inorgchem.7b02171

    • Related Report
      2017 Annual Research Report
    • Peer Reviewed / Int'l Joint Research
  • [Presentation] Calorimetric Evidence of d-wave pairing in κ- and λ-type Organic superconductors2018

    • Author(s)
      S. Imajo
    • Organizer
      International Symposium for Structural Thermodynamics
    • Related Report
      2017 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Low temperature electronic states of organic superconductors2017

    • Author(s)
      S. Imajo
    • Organizer
      International Symposium for Structural Thermodynamics-Young Thermodynamicists
    • Related Report
      2017 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Superconductivity Occurred in Organics2017

    • Author(s)
      S. Imajo
    • Organizer
      Interdisciplinary Symposium for Up-and-Coming Material Scientists (ISUMS 2017)
    • Related Report
      2017 Annual Research Report
    • Int'l Joint Research
  • [Presentation] β”型有機導体における低温電子相図2017

    • Author(s)
      今城周作,圷広樹,A. L. Morritt,L. Martin,中澤康浩
    • Organizer
      第11回分子科学討論会2017
    • Related Report
      2017 Annual Research Report
  • [Presentation] Low temperature electronic phase diagram of β"-type organic conductors2017

    • Author(s)
      S. Imajo, Hiroki Akutsu, , A. L. Morritt, L. Martin, and Y. Nakazawa
    • Organizer
      12th International Symposium on Crystalline Organic Metals, Superconductors and Magnets
    • Related Report
      2017 Annual Research Report
    • Int'l Joint Research
  • [Presentation] 電荷ゆらぎ超伝導状態の低温電子熱容量2017

    • Author(s)
      今城周作,山下智史,圷広樹,中澤康浩
    • Organizer
      第53回熱測定討論会
    • Related Report
      2017 Annual Research Report
  • [Presentation] Low temperature electronic state of β"-type organic conductors2017

    • Author(s)
      S. Imajo, Hiroki Akutsu, Y. Nakazawa, A. L. Morritt, and L. Martin
    • Organizer
      Multiscale phenomena in molecular matter 2017
    • Related Report
      2017 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Thermodynamic Study of FFLO State Occurred in the Organic Superconductor λ-(BETS)2GaCl42017

    • Author(s)
      S. Imajo, S. Yamashita, H. Akutsu, H. Kumagai, T. Kobayashi, A. Kawamoto, and Y. Nakazawa
    • Organizer
      The 72th Calorimetry Conference
    • Related Report
      2017 Annual Research Report
    • Int'l Joint Research
  • [Funded Workshop] Multiscale phenomena in molecular matter 20172017

    • Related Report
      2017 Annual Research Report
  • [Funded Workshop] The 72th Calorimetry Conference2017

    • Related Report
      2017 Annual Research Report

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Published: 2017-05-25   Modified: 2024-03-26  

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