| 研究実績の概要 |
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 accompanied by insulator-to-metal transitions arising from the simultaneous presence of the electronically-active C60 sublattice. We developed robust routes to isolate and structurally and electronically characterize at both ambient and elevated pressures the ternary systems, (Sm1-xMx)2.75C60 (M = Ca, Eu; 0 <= x <= 1) in which the Sm valence change is quasi-continuously controlled chemically by either the valence-precise Ca2+ ion or the mixed valent Eu2+/3+ ion. This has led to families of mixed valence materials with chemically and 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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