2018 Fiscal Year Annual Research Report
Emergent electronic phenomena in hybrid f-/p-electron molecular materials
Publicly Offered Research
| Project Area | J-Physics: Physics of conductive multipole systems |
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| Project/Area Number |
18H04303
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| Research Institution | Osaka Prefecture University |
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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)
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| Project Period (FY) |
2018-04-01 – 2020-03-31
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| Keywords | rare earths / mixed valence / fullerides / Kondo insulators / high pressure / synchrotron X-rays |
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| Outline of Annual Research Achievements |
The project has focused on research in emergent electronic phenomena in the family of hybrid f-/p-electron molecular materials successfully established for the first time by our work to-date within J-Physics. In order to achieve our targets, we synthesized and researched new families of molecular-based strongly correlated f-electron fullerides in which the presence of the electronically-active C60 anions is combined with mixed configuration rare earths such as Sm or Eu leading to properties intrinsically unattainable in any other system currently available. Strong correlations dominate the electronic properties of both the rare-earth cation and the C60 anion sublattices. To-date the project has unambiguously authenticated by both synchrotron X-ray diffraction and element-specific spectroscopic techniques at ambient and elevated pressures the occurrence of valence transitions with novel characteristics arising from the simultaneous presence of the electronically-active C60 sublattice. We developed robust routes to isolate and structurally characterize the ternary systems, (Sm1-xCax)2.75C60 (0 <= x <= 1) in which the valence change is quasi-continuously controlled chemically by the valence-precise Ca2+ ion. This has led to a family of mixed valence materials with chemically (and potentially physically) quasi-continuously tunable valence transitions opening up the possibility of unveiling a new type of quantum criticality caused by critical valence fluctuations.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Progress is extremely satisfactory with new unanticipated directions and new opportunities having appeared. Work on f-electron fullerides has led to families of new materials and new properties are emerging. The wealth of hybrid f-/p-electron families of molecular materials chemically synthesized in this work has led to numerous investigations of the fragility of the electronic states with changes in external stimuli such as temperature and pressure. This has necessitated the use of a panoply of experimental techniques at both ambient and elevated pressures, including synchrotron X-ray diffraction, optical spectroscopy, magnetometry and synchrotron X-ray absorption spectroscopy in its high-resolution partial-fluorescence-yield (PFY-XAS) variant.
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| Strategy for Future Research Activity |
Future research plans continue to focus on discovery of new materials and isolation of new electronic states. Emphasis will continue to be placed on the synthesis of new families of strongly correlated f-electron fullerides but we will also tackle more complex materials both synthetically and electronically. These will include superconducting ternary metal fullerides. Here we will synthesize binary alkaline-earth superconductors with closed-shell alkaline-earth metal ions. We will then introduce in the metal sites configurationally active rare-earth cations to synthesize the ternary phases. In this way, we will chemically introduce the prospect of coexisting superconductivity supported by the C60-based electrons and Kondo phenomena associated with the rare earth ions. We will then attempt to probe the stability of the superconducting state with changes in the filling of the fulleride conduction band driven by configuration transitions at the lanthanide dopants.
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