Research of Competition and Coexistence of Charge-ordered and Superconducting States in Novel Organic Superconductors

新型有机超导体中电荷有序态与超导态的竞争与共存研究

基本信息

批准号：
17540315
负责人：
MORI Hatsumi
金额：
$ 1.99万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

In order to investigate the relationship between charge ordering and superconductivity for novel organic superconductor beta-(meso-DMBEDT-TTF)_2PF_6, the detailed measurements of electrical resistivity and magnetoresistivity have been carried out.Our results are followings.(1) Determination of superconducting state by measurements of electrical and magnetoresistivity under pressureThe detailed measurements of electrical resistivity under pressure revealed that the resistance drop of observed at Tc(onset) = 4.6 K under relatively low pressure 0.6 kbar, whose superconductivity was confirmed by applying magnetic field. The superconducting phase extends widely to Tc=2.6K under 5.2 kbar.(2) Determination of charge-ordered state by temperature and magnetic field dependences of magnetoresistance under pressure The temperature dependence of resistivity for beta-(meso-DMBEDT-TTF)_2PF_6 is peculiar under 0.6 kbar; the resistivity minimum is observed at 60K, the increase of resistivity by 8 times with lowering temperature, and the sudden drop of resitivity is observed at 4.6K. The raman spectroscopy under pressure demonstrates that the resistivity increase is originated by charge ordering (CO). In this CO region, large magnetoresistance was observed, its increasing rate (ΔR/R(0T)) increases with applying pressure, and in even the metallic state at low temperatures, the magnetoresistance can be observed. Therefore, the illustrated P-T phase diagram reveals that the static and dyanimical CO states exist in neighbouring of superconducting state, which is the first experimental observation among molecular superconductors.

为了研究新型有机超导体β-(meso-DMBEDT-TTF)_2PF_6的电荷有序性与超导性之间的关系，对电阻率和磁阻率进行了详细的测量，结果如下：(1)超导性的测定通过测量压力下的电阻率和磁阻率来确定状态压力下电阻率的详细测量表明，在 Tc(onset) = 4.6 时观察到的电阻降K在相对较低的压力0.6 kbar下，通过施加磁场证实了其超导性，在5.2 kbar下超导相广泛延伸至Tc=2.6K。(2)通过压力下磁阻的温度和磁场依赖性确定电荷有序态。 beta-(meso-DMBEDT-TTF)_2PF_6 的电阻率温度依赖性在 0.6 kbar 下是特殊的；观察到电阻率最小值；在 60K 时，随着温度的降低，电阻率增加了 8 倍，并且在 4.6K 时观察到电阻率突然下降，表明电阻率的增加是由电荷有序 (CO) 引起的。观察到大的磁阻，其增加率(ΔR/R(0T))随着施加压力而增加，并且即使在低温下的金属状态下，也可以观察到磁阻。图解的P-T相图揭示了超导态附近存在静态和动态CO态，这是分子超导体中首次实验观察到。