Thermodynamic Investigation of the Gap Structure and Electron Pair-Symnetry in Organic Superconductors

有机超导体中的带隙结构和电子对对称性的热力学研究

• 批准号: 09640450
• 负责人: NAKAZAWA Yasuhiro
• 金额: $ 2.05万
• 依托单位: Okazaki National Research Institutions
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640450/
• 关键词: Superconductivety; Specific Heat; Organic Conductor; 有機伝導体; 有機超伝導体; 準粒子励起

This research project aims at clarifying the structure of energy gap in the superconductive states of BEDT-TTF based organic superconductors through analyses of specific heat data. To get detail information on the ground state and the low-energy excitations from it, we performed the experiment at extremely low-temperature region below IK. We have improved a sample cell for the thermal-relaxation type calorimeter equipped with the dilution refrigerator at Institute for Molecular Science. As a consequence, we have succeeded to reduce the heat capacity of addenda part down to about 0.1μJ/K at 1K, which is satisfactory small to get enough resolution. For the system of κ-(BEDT-TTF)ィイD22ィエD2X [X=Cu[N(CN)ィイD22ィエD2]Br, Cu(NCS)ィイD22ィエD2] ,we have discussed the temperature dependence of specific heat and magnetic fields dependence of electronic specific-heat coefficient, γ up to 10T and also discuss the residual γ* term in the superconductive state. The results suggest that the gap-structure of this system can be explained within the frame of line-nodes picture of d-wave superconductors. It is however to be mentioned that the γ(H) curves of both salts show a kink around 2T, which may be related to the vortex states of these materials. We are going to further inquire into the magnetic fields dependence of this γ in order to clarify the pairing nature and vortex state in detail.

该研究项目旨在通过分析比热数据来阐明基于BEDT-TTF的有机超导体超导态的能隙结构。为了获得基态及其低能激发的详细信息，我们在 IK 以下的极低温区域进行了实验。我们改进了分子科学研究所配有稀释制冷机的热弛豫式热量计的样品池。因此，我们成功地将附加部分的热容降低至 1K 时的约 0.1μJ/K，这足以获得足够的分辨率。对于κ-(BEDT-TTF)ィイD22ィエD2X [X=Cu[N(CN)ィイD22ィエD2]Br, Cu(NCS)ィイD22ィエD2]体系，我们讨论了电子比热系数的温度依赖性和磁场依赖性，γ高达10T，还讨论了剩余γ*项处于超导状态。结果表明，该系统的能隙结构可以在 d 波超导体线节点图的框架内得到解释。然而值得注意的是，两种盐的 γ(H) 曲线在 2T 附近表现出扭结，这可能与这些材料的涡旋态有关。我们将进一步研究该 γ 的磁场依赖性，以便详细阐明配对性质和涡旋状态。

项目成果

Y. Nakazawa and K. Kanoda: "Thermodynamic Investigation on of the Electoronic States of Deuterated k-(BEDT-TTF)_2X _2"Physical Review B. 60. 4263-4267 (1999)

Y. Nakazawa 和 K. Kanoda：“氘代 k-(BEDT-TTF)_2X _2 电子态的热力学研究”物理评论 B. 60. 4263-4267 (1999)

H.Taniguchi,A.Kawamoto,Y.Nakazawa and K.Kanoda: "Metal-Insalater Tnansition in Partially Deuterated K-(BEDT-TTF)_2 Cu[N(CN)_2]Br" Synthetic Metals. (印刷中). (1999)

H. Taniguchi、A. Kawamoto、Y. Nakazawa 和 K. Kanoda：“部分氘化 K-(BEDT-TTF)_2 Cu[N(CN)_2]Br 中的金属-Insalater Tnansition”（正在出版）。 (1999)

Y. Nakazawa and k. Kanoda: "Low-Temperature Specific Heat Studies on Superconductors and Mtt Insulators in k-(BEDT-TTF)2X System"Synthetic Metals. 85. 1563-1564 (1997)

Y.中泽和k。

H. Taniguchi, Y. Nakazawa and K. Kanoda: "Phase Diagram of Vortices in the Quasi-Two-Dimensional Organic Superconductor a-(BEDT-TTF)2NH4HG(SCN)4: A System of Pancake Vortices with Out-of-Plane Coupling Dominated by the Electromagnetic Energy"Phys. Rev.. B

H. Taniguchi、Y. Nakazawa 和 K. Kanoda：“准二维有机超导体 a-(BEDT-TTF)2NH4HG(SCN)4 中涡旋的相图：面外薄饼涡旋系统

Y. Nakazawa and k. Kanoda: "Thermodynamic Investigation of the Electronic States of Deuterated k-(BEDT-TTF)2CU[N(CN)2]Br"Phys. Rev.. B60. 4263-4267 (1999)

Y.中泽和k。