2022 Fiscal Year Annual Research Report
Development of new high Tc superconductors through internal and external dual-direction doping of carbon superatoms
| Project/Area Number |
18K18724
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| Research Institution | Osaka Metropolitan University |
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Principal Investigator |
プラシデス コスマス 大阪公立大学, 大学院工学研究科, 教授 (90719006)
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| Project Period (FY) |
2018-06-29 – 2023-03-31
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| Keywords | Superconductivity / Molecular nanocarbons / Endohedral fullerene / Dual doping / Magnetism |
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| 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.
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