Synthesis and phase control of fullerene based superstructured materials

富勒烯基超结构材料的合成与相控制

• 批准号: 15340106
• 负责人: TAGUCHI Yasujiro
• 金额: $ 9.22万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15340106/
• 关键词: fullerene; alkali metal intercalation; insulator-superconductor transition; solid solution; electronic specific heat; density of states; Jahn-Teller interaction; orbital degeneracy; ヤン・テラー相互作用; 金属内包フラーレン; 薄膜; 電界効果トランジスター; 光吸収スペクトル; ホッピング伝導

In this fiscal year, we have tried to reveal universality and unique points in fullerene based compounds, dealing with layered nitride superconductors that also exhibit band insulator to superconductor transition similarly to the case of alkali metal intercalated fullerides. We have succeeded in preparing a series of samples with continuously changed Li-content (x<0.12), and have confirmed that these are of single phase by using synchrotron X-ray diffraction technique at BL2B-02, SPring 8. This fact makes striking contrast with the case of fullerides where only line phases exist and the intermediate phases can not be obtained, clearly indicating the anomalous solid state chemistry of fullerene compounds. Also, we have performed the specific heat measurements of layered nitride superconductors in magnetic fields, and have found that the normal-state Sommerfeld constant γ is very small (=1.0 mJ/mol K^2). We can obtain very small electron-phonon coupling constant λ(=0.22) by using this value and the density of states at the Fermi level predicted by several band calculations. This fact is in accord with the relatively narrow phonon lines observed in Raman scattering spectra. This fact also makes striking contrast with the fullerides where superconductivity is mediated by high frequency phonon with intermediate electron-phonon coupling strength, indicating the importance of Jahn-Teller interaction where the fullerene molecules show deformation. It is theoretically pointed out that Jahn-Teller interaction that couples with the degenerate LUMO orbitals is important in fullerides, and our result is consistent with this.

在本财政年度，我们试图揭示富勒烯基化合物的普遍性和独特性，处理层状氮化物超导体，这种超导体也表现出与碱金属嵌入富勒化物类似的带绝缘体到超导体的转变。我们成功地制备了一系列li含量连续变化（x<0.12）的样品，并通过同步加速器x射线衍射技术在BL2B-02， SPring 8上证实了这些样品是单相的。这一事实与富勒烯中只存在线相而不能得到中间相的情况形成鲜明对比，清楚地表明富勒烯化合物的异常固态化学性质。此外，我们还进行了层状氮超导体在磁场中的比热测量，发现正常状态的索默菲尔德常数γ非常小（=1.0 mJ/mol K^2）。利用该值和几种能带计算预测的费米能级态密度，我们可以得到非常小的电子-声子耦合常数λ(=0.22)。这与拉曼散射光谱中观测到的相对狭窄的声子线是一致的。这一事实也与富勒烯形成鲜明对比，其中超导性是由高频声子介导的，具有中间电子-声子耦合强度，表明了Jahn-Teller相互作用的重要性，其中富勒烯分子表现出变形。从理论上指出与简并LUMO轨道耦合的Jahn-Teller相互作用在富勒化物中是重要的，我们的结果与此一致。

项目成果

Chemical control of spin chirality in (Nd_<1-x>Dy_x)_2Mo_2O_7

(Nd_<1-x>Dy_x)_2Mo_2O_7自旋手性的化学控制

• 发表时间: 2004
• 期刊: Phys.Rev.B 69
• 作者: Matsumoto;Tomoaki;J.H.Jung;S.Iguchi et al.
• 通讯作者: S.Iguchi et al.

Orbital ordering near a Mott transition : Resonant x-ray scattering study of the perovskite Ti oxides RTiO_3 and LaTiO_<3.02> (R=Gd, Sm, Nd and La)

莫特跃迁附近的轨道排序：钙钛矿钛氧化物 RTiO_3 和 LaTiO_<3.02>（R=Gd、Sm、Nd 和 La）的共振 X 射线散射研究

• 发表时间: 2004
• 期刊: Phys.Rev.B 70
• 作者: J.H.Jung et al.;T.Gotoh et al.;M.Kubota et al.
• 通讯作者: M.Kubota et al.

Y.Taguchi et al.: "Magnetic field induced sign reversal of the anomalous Hall effect in a pyrochlore ferromagnet Nd2Mo2O7 : Evidence for a spin chirality mechanism"Physical Review Letters. 90. 257202-1-257202-4 (2003)

Y.Taguchi 等人：“烧绿石铁磁体 Nd2Mo2O7 中异常霍尔效应的磁场诱导符号反转：自旋手性机制的证据”物理评论快报。

Charge dynamics near the electron-correlation induced metal-insulator transition in pyrochlore-type molybdates.

• DOI: 10.1103/physrevlett.93.266401
• 发表时间: 2004-12
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: I. Kézsmárki;N. Hanasaki;D. Hashimoto;S. Iguchi;Y. Taguchi;S. Miyasaka;Y. Tokura

High-pressure study of layered nitride superconductors

层状氮化物超导体的高压研究

• 发表时间: 2004
• 期刊: Phys.Rev.B 70
• 作者: Y.Kaneko et al.;Y.Taguchi et al.
• 通讯作者: Y.Taguchi et al.