| Co-Investigator(Kenkyū-buntansha) |
OTSUKA Akihiro Kyoto Univ. Graduate School of Sci., Instructer, 大学院・理学研究科, 助手 (90233171)
BAN Toshio Kyoto Univ. Graduate School of Sci., Instructer, 大学院・理学研究科, 助手 (10025372)
YAMOCHI Hideki Kyoto Univ. Graduate School of Sci., Asso.Prof., 大学院・理学研究科, 助教授 (20182660)
KONDO Tetsuo Kyoto Univ. Graduate School of Sci., Instructer, 大学院・理学研究科, 助手 (20283583)
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| Research Abstract |
1) The anion layer of a Mott insulator κ-(BEDT-TTF)ィイD22ィエD2CuィイD22ィエD2(CN)ィイD23ィエD2 is composed of infinite zigzag polymer chains of (CN-Cu)ィイD2nィエD2 and disordered [NC]ィイD1-1ィエD1 anion which connects the infinite chains. A replacement of the half of (CN-Cu)ィイD2nィエD2 and whole disordered CN groups by [NC-N-CN]ィイD1-1ィエD1 groups of it provided a superconductor κ-(BEDT-TTF)ィイD22ィエD2Cu(CN)[N(CN)ィイD22ィエD2] with Tc =11K. Numbers of superconductors having Tc in the range of 3K〜10.5K were prepared by the partial replacement. At the same time, some CuィイD1+1ィエD1 ions were substituted by CuィイD1+2ィエD1 ions. Consequently the system was found to be formulated as κ-(BEDT-TTF)ィイD22ィエD2(CuィイD1+1ィエD1)ィイD22-x-yィエD2(CuィイD1+2ィエD1)ィイD2xィエD2(CN)ィイD23-2yィエD2[N(CN)ィイD22ィエD2]ィイD2yィエD2, where y took mainly 0.05, 0.3〜0.4 and 0.8 and x=0〜1600 ppm. The anion [N(CN)ィイD22ィエD2]ィイD1-1ィエD1 was found to distribute homogeneously in the anion layer. The single crystal of y = 0.3〜0.4 exhibited varied Tc's of 3.1, 6.5, 7.5,
… More
8.8 and 10.2 K.
2) Using the same electrolyte for κ-(BEDT-TTF)ィイD22ィエD2(CuィイD1+1ィエD1)ィイD22-x-yィエD2(CuィイD1+2ィエD1)ィイD2xィエD2(CN)ィイD23-2yィエD2[N(CN)ィイD22ィエD2]ィイD2yィエD2, some crystals with different shape were obtained and showed the superconductivity (Tc=11K). The lattice parameters of the crystals indicated θ-type structure.
3) The metallic behavior down to 2〜3 K was observed in the BEDT-TTF salts the organic anions of tetranitrobiphenol dianion or tetracyanoallylide anions(RO-TCAィイD1-ィエD1). The Mott insulators of BEDT-TTF with the flexible anion, RO-TCAィイD1-ィエD1 transformed into the metallic complexes on the removal of the solvent of crystallization. The BEDT-TTF complex with the anion consists of a transition metal and dithiooxalate gave a semimetallic complex which shows the abrupt decrease of the resistivity on cooling under the pressure of 4.7 kbar (onset 7 K). The occurrence of the superconductivity is now being examined.
4) To examine the controlling of the bandwidth of the complexes, EOET, which is the hybrid molecule between BEDT-TTF and BEDO-TTF, was employed for complex formation. As the application of the self-assembling property of BEDO-TTF, the colorless metallic films were prepared by doping halogens to the films of 1 wt% of BEDO-TTF and polycarbonate composite.
5) The Raman spectroscopic study of alkali doped OMTTF・CィイD260ィエD2 complexes revealed that the occurrences of their superconductivities require the anion species of CィイD260ィイD12-ィエD1ィエD2 and CィイD260ィイD13-ィエD1ィエD2 when the pristine complex is doped with Rb and K, respectively. With the CィイD260ィエD2CIィイD26ィエD2, CィイD260ィエD2BrィイD2xィエD2(x=6, 8) which are stronger electron acceptors than CィイD260ィエD2, the preparation of the complexes of organic donor molecules were examined.
6) We have started the investigations to prepare organic superconductors of new categories, which consist of the alternating stack or D-π-A type molecule. The first metallic complex of the alternating stack was prepared (HMTTeF・EtィイD22ィエD2TCNQ・THFx). Also, the degrees of intramolecular charge-transfer(γ) were examined on the series of DィイD1+YィエD1-π-AィイD1-YィエD1 type molecules. Less
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