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2021 Fiscal Year Research-status Report

Development of new high Tc superconductors through internal and external dual-direction doping of carbon superatoms

Research Project

Project/Area Number 18K18724
Research InstitutionOsaka Prefecture University

Principal Investigator

プラシデス コスマス  大阪府立大学, 工学(系)研究科(研究院), 教授 (90719006)

Project Period (FY) 2018-06-29 – 2023-03-31
KeywordsSuperconductivity / Molecular nanocarbons / Endohedral fullerene / Dual doping / Magnetism
Outline of Annual Research Achievements

Most superconductors have simple structures built from atoms, but superconductors made from molecules arranged in solid structures also exist. Prominent examples are those of nanocarbon superatoms, the fullerenes (C60) - they show the highest superconducting transition temperature, Tc (38 K) and do not lose their zero resistance performance even under extremely high magnetic fields (>90 Tesla). In this research, we are using a new building block for molecular superconductors beyond C60. This is [Li@C60], an endohedral metallofullerene, which incorporates a Li+ ion inside the C60- cage. We have developed a scalable method to obtain neutral Li+@C60(-) by chemical reduction of Li+@C60 using decamethylferrocene. Investigation of solid [Li@C60] revealed the presence mainly of dimers (Li@C60)2, together with the co-existence of a small fraction of the EPR-active monomer form. However, although this preparative route does not demand long reaction times, it leads to poorly crystalline materials. This is unlike electrolytic reduction routes, which afford very crystalline materials but in small quantities. Nonetheless this allows the in-depth structural characterization, which has unveiled a highly symmetric hexagonal crystal structure comprising disordered dimer units in analogy with (C59N)2 or molecular dihydrogen. To date, we have achieved a full structural characterization of the structural properties of the endohedral metallofullerene as a function of temperature down to liquid helium temperatures and as a function of pressure up to applied hydrostatic pressures of 12 GPa.

Current Status of Research Progress
Current Status of Research Progress

1: Research has progressed more than it was originally planned.

Reason

Superconductors have no electrical resistance and carry electricity without losing energy. The development of new materials in order to achieve
transition temperatures to zero-resistance as high as possible is at the extreme forefront of current challenges in materials science. C60 superconductors played leading role in materials research in the last 30 years achieving a robust zero-resistance state at record temperatures and surviving at extremely high magnetic fields. But they have reached their upper limit. Here we are facing the challenge of surpassing the past performance of C60 superconductors. We are targeting to achieve this by developing the uncharted field of high-symmetry superatomic carbon frameworks with metal ions inside the cages and using unprecedented mechanisms of electronic control by dual-direction internal and external electron doping. This is a challenging proposal because there are simply no systems of this type created before and, if and when made, theory
predicts superb performance. Currently we have achieved the first milestone of producing and characterizing in the bulk the parent neutral lithium endohedral C60 fullerene both as a function of temperature and pressure - this constitutes the starting material, the synthon of our eventual targets and confirms that we are progressing at a good pace for this research.

Strategy for Future Research Activity

Our research plan follows two complementary procedures: (i) to develop the new synthetic chemistry needed, and (ii) to combine it with advanced structural and physical property measurements and feedback from theory. The research will include: [1] Synthesis of dual-direction-doped A+n[Li+@C60(n+1)-] phases (A = alkali metal; n = 1-6). This will define the full range of valences and electronic ground states in C60 cages dually-electron-doped internally and externally. [2] Physical control of structure and properties. Application of pressure will be used to drive insulator-to-metal transitions and trigger the emergence of superconductivity out of non-superconducting A+n[Li+@C60(n+1)-] precursors away from half filling of the conduction band. [3] Electronic and magnetic ground states in the new materials. The strong interplay between crystal and electronic structure requires the use of many advanced experimental techniques at both ambient and elevated pressures. We have the expertise to
employ the full range of experimental techniques to investigate crystal structure (synchrotron X-ray & neutron diffraction), electronic
structure (magnetometry, transport properties, specific heat) and dynamics (NMR/muSR/EPR & IR/Raman spectroscopy) throughout the project
duration. The integrated study of structure and electronic properties in the normal and superconducting states will be the basis for theoretical
understanding of the new metallic/superconducting ground states.

Causes of Carryover

The original targets of this research project were rapidly achieved and we were proceeding in targeting the availability of the endohedral metallofullerene materials in large-quantities to allow full exploratory synthesis. The next steps involved more elaborate structural and physical characterization as a function of temperature as well as the utilization of high pressure to enhance the properties. Progress along these lines was severely impeded by the coronavirus pandemic. We anticipate that the resources necessary to proceed with the implementation, including those carried over will allow completion of the project.

  • Research Products

    (18 results)

All 2022 2021 Other

All Int'l Joint Research (3 results) Journal Article (1 results) (of which Int'l Joint Research: 1 results,  Peer Reviewed: 1 results) Presentation (13 results) (of which Int'l Joint Research: 7 results,  Invited: 3 results) Remarks (1 results)

  • [Int'l Joint Research] ESRF, Grenoble(フランス)

    • Country Name
      FRANCE
    • Counterpart Institution
      ESRF, Grenoble
  • [Int'l Joint Research] Charles University, Prague(チェコ)

    • Country Name
      CZECH
    • Counterpart Institution
      Charles University, Prague
  • [Int'l Joint Research] Bursa Technical University(トルコ)

    • Country Name
      TURKEY
    • Counterpart Institution
      Bursa Technical University
  • [Journal Article] Pressure effects on the crystal structure of the cubic metallofullerene salt [Li@C60][PF6] to 12 GPa2022

    • Author(s)
      Colman Ross H.、Esma Okur H.、Garbarino Gaston、Ohishi Yasuo、Aoyagi Shinobu、Shinohara Hisanori、Prassides Kosmas
    • Journal Title

      Materials Today Communications

      Volume: 31 Pages: 103275~103275

    • DOI

      10.1016/j.mtcomm.2022.103275

    • Peer Reviewed / Int'l Joint Research
  • [Presentation] Emergent electronic phenomena in all-carbon π-electron molecular systems2021

    • Author(s)
      Kosmas Prassides
    • Organizer
      Joint seminars of the Department of Condensed Matter Physics (DCMP) and the Materials Growth and Measurement Laboratory (MGML), Charles University, Prague, Czech Republic
    • Invited
  • [Presentation] Valence tuning in rare-earth fullerides at ambient and elevated pressures2021

    • Author(s)
      Naoya Yoshikane, Kosmas Prassides
    • Organizer
      American Chemical Society ACS Spring 2021 meeting
    • Int'l Joint Research
  • [Presentation] Crystal structure of cation-ordered ternary fullerides M2AC602021

    • Author(s)
      Keisuke Matsui, Kosmas Prassides
    • Organizer
      Summer School 2021, Young Coordination Chemists Association of Japan
  • [Presentation] Structural and electronic studies of rare-earth fullerides at elevated pressures2021

    • Author(s)
      Naoya Yoshikane, Kosmas Prassides
    • Organizer
      Summer School 2021, Young Coordination Chemists Association of Japan
  • [Presentation] Systematic structural study of cation-ordered pentavalent fullerides2021

    • Author(s)
      Keisuke Matsui, Kosmas Prassides
    • Organizer
      The 61st Fullerenes-Nanotubes-Graphene General Symposium
  • [Presentation] Synthesis and structural study of non-cubic cation-ordered ternary fullerides M2AC602021

    • Author(s)
      Keisuke Matsui, Kosmas Prassides
    • Organizer
      2021 Autumn Meeting, The Physical Society of Japan
  • [Presentation] Structural and electronic study of rare-earth fullerides by synchrotron XAS and XRD techniques at ambient and elevated pressures2021

    • Author(s)
      Naoya Yoshikane, Kosmas Prassides
    • Organizer
      2021 Autumn Meeting, The Physical Society of Japan
  • [Presentation] Tuning of Mixed Valency in Rare-Earth Fullerides at Ambient and Elevated Pressures2021

    • Author(s)
      Naoya Yoshikane, Kosmas Prassides
    • Organizer
      2021 Materials Research Society (MRS) Fall Meeting
    • Int'l Joint Research
  • [Presentation] Crystal Structure and Electronic Properties of Cation-Ordered Non-Cubic Pentavalent Fullerides2021

    • Author(s)
      Keisuke Matsui, Kosmas Prassides
    • Organizer
      2021 Materials Research Society (MRS) Fall Meeting
    • Int'l Joint Research
  • [Presentation] Tuning rare-earth mixed valency by coupling to electronically-active fulleride anion sublattices2021

    • Author(s)
      Naoya Yoshikane, Kosmas Prassides
    • Organizer
      PACIFICHEM 2021, The International Chemical Congress of Pacific Basin Societies 2021
    • Int'l Joint Research
  • [Presentation] Spontaneous magnetoelastic effects in Prussian blue analogue molecular magnets2021

    • Author(s)
      Tomoaki Fushimi, Kosmas Prassides
    • Organizer
      PACIFICHEM 2021, The International Chemical Congress of Pacific Basin Societies 2021
    • Int'l Joint Research
  • [Presentation] Mixed valency in alkali sesquioxides2021

    • Author(s)
      Kosmas Prassides
    • Organizer
      PACIFICHEM 2021, The International Chemical Congress of Pacific Basin Societies 2021
    • Int'l Joint Research / Invited
  • [Presentation] Quantum magnetism in fully-frustrated all-carbon pi-electron systems2021

    • Author(s)
      Kosmas Prassides
    • Organizer
      PACIFICHEM 2021, The International Chemical Congress of Pacific Basin Societies 2021
    • Int'l Joint Research / Invited
  • [Remarks] Electronic Functional Materials Laboratory

    • URL

      http://mtr1.osakafu-u.ac.jp/prassides-lab/

URL: 

Published: 2022-12-28  

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