Novel Electronic States in the Soft Lattice of Organic Conductors from the Control to the Design of Electronic States

有机导体软晶格中的新型电子态从电子态的控制到设计

• 批准号: 10102004
• 负责人: KAGOSHIMA Seiichi
• 金额: $ 92.48万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Specially Promoted Research
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10102004/
• 关键词: Organic conductor; Organic superconductor; Uniaxial compression; Uniaxial strain; Superconductivity; Magnetoresistance; X-ray diffraction; 有機超伝導; 極低温X線回折; 電子状態; 低温X線回析; 電荷密度波; スピン密度波; 一軸性加圧; 低温X線回折; 熱電能

Organic conductors are soft and suffer changes in crystal structure of not only the molecular position but also the molecular orientation. The purpose of this study is to reveal the relationship between changes in crystal structure and electronic properties of organic conductors at low temperature under structural controls by "uniaxial compression". This leads to a control and a design of organic compounds, which have a rich variety in structure and electronic properties.We succeeded to develop the experimental method of uniaxial compression for transport and low-temperature x-ray diffraction measurements. Using this method, we measured electrical resistance, magnetoresistance and low temperature crystal structure of quasi two-dimensional conductors α-(BEDT-TTF)_2XHg(SCN)_4 where X=K and X=NH_4. In relation to superconductivity, we found an increase in the superconducting critical temperature from 1.5K of ambient pressure to 6K under the uniaixial compression parallel to the c-axis. Th … More e electronic structure derived by x-ray structure analyses was found to be semi-quantitatively consistent with theoretical expectation for the critical temperature by BCS theory. This result remonstrated the feasibility of the uniaxial compression method for the first time. We discovered also a novel magnetoresistance phenomenon in studies at hydrostatic pressures and named it "small closed-orbit effect".We measured also uniaxial strain effects in related materials like the β- and θ-type BEDT-TTF series and BO series of organic conductors. Changes in electronic properties were found to occur as expected. However, we discovered some novel phenomena to be investigated in future studies. We tried also a material design using organic acceptors to succeed in synthesizing original organic superconductor (BETS)_2(Cl_2TCNQ). This is the first organic superconductor composed of only organic molecules.The uniaxial strain method developed in this research is expected to be useful in controlling Coulomb correlation between electrons and to be applied also to magnetic and optical measurements. Less

有机导体是软的，并且不仅分子位置而且分子取向的晶体结构发生变化。本研究的目的是揭示“单轴压缩”结构控制下有机导体在低温下晶体结构变化与电子性能之间的关系。这导致了有机化合物的控制和设计，它们具有丰富的结构和电子特性。我们成功开发了用于输运和低温X射线衍射测量的单轴压缩实验方法。利用该方法，我们测量了准二维导体α-(BEDT-TTF)_2XHg(SCN)_4（其中X=K和X=NH_4）的电阻、磁阻和低温晶体结构。关于超导性，我们发现在平行于 c 轴的单轴压缩下，超导临界温度从环境压力的 1.5K 增加到 6K。通过X射线结构分析得出的电子结构被发现与BCS理论对临界温度的理论预期半定量一致。这一结果首次证明了单轴压缩方法的可行性。我们在静水压力的研究中还发现了一种新的磁阻现象，并将其命名为“小闭轨效应”。我们还测量了相关材料的单轴应变效应，例如β型和θ型BEDT-TTF系列以及BO系列有机导体。发现电子特性的变化如预期发生。然而，我们发现了一些新现象，需要在未来的研究中进行研究。我们还尝试了使用有机受体的材料设计，成功合成了原始有机超导体（BETS）_2（Cl_2TCNQ）。这是第一个仅由有机分子组成的有机超导体。本研究中开发的单轴应变方法预计可用于控制电子之间的库仑相关性，并可应用于磁和光学测量。较少的

项目成果

鹿児島誠一: "Low-Temperature Diffuse X-ray Studies of Charge-Density Waves Coexisting with Spin-Density Waves in the Organic Conductors (TMTSF)_2PF_6 and (TMTSF)_2AsF_6"Solid State Communications. 110. 479-483 (1999)

Seiichi Kagoshima：“有机导体中与自旋密度波共存的电荷密度波的低温漫射 X 射线研究 (TMTSF)_2PF_6 和 (TMTSF)_2AsF_6”固态通信。 110. 479-483 (1999)