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

基本信息

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

项目摘要

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.

本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，我们进行了实验。在低于IK的极低温区域，我们改进了分子科学研究所配有稀释制冷机的热弛豫型热量计的样品池，从而成功地降低了热容。附录部分在 1K 时降至约 0.1μJ/K，对于 κ-(BEDT-TTF)D22D2X [X=Cu[N(CN)D22] 系统来说，这是令人满意的小值，我们已经讨论了温度。比热和磁场的依赖性电子比热系数的依赖性，γ 高达10T 并讨论了超导状态下的剩余 γ* 项，结果表明该系统的间隙结构可以在 d 波超导体的线节点图的框架内进行解释。两种盐的 γ(H) 曲线在 2T 附近显示出扭结，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，以澄清这一点。详细配对自然和涡旋状态。