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Research on superconductivity transition phenomena of organic conductor through quantum oscillation effects.

通过量子振荡效应研究有机导体的超导跃迁现象。

基本信息

批准号：
12640342
负责人：
ITO Hiroshi
金额：
$ 2.3万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

Organic superconductor K, -(BEDT-TTEOsCuCNCS^ exhibits superconducting fluctuation effects enhanced by the inherent layered structure. As a result, the superconductivity transition is smeared with no distinct upper critical field. In order to get insight into the superconductivity transition characteristics, damping due to superconductivity appearing on the quantum oscillations is studied.Superconductivity damping factor appearing on the de Haas-van alphen effect, which was measured as a collaboration project with University of Bristol, is analyzed in terms of the superconducting fluctuation. Up to 0.5K, fluctuating superconductivity gap is clarified quantitatively. Its angle dependence with respect to the direction of the external magnetic field indicates the two-dimensionality of the superconductivity and relevant fluctuation effects. In order to investigate the correlation with the two-dimensionality in the normal state, temperature dependence of the anisotropy of resistivity is measured.The Shubnikovde Haas effect, the quantum oscillation on the resistivity, is measured at ambilent and 2 kbar pressure, under temperature down to 0.55 K and magnetic field up to 9 T generated by the magnet purchased with the grant. The Shubnikovde Haas effect is observed above 6.8 T. In a magnetic field region between 6.8 and 7.3 T, additional damping of the oscillation is found. Under pressure in which superconductivity is suppressed, the damping is absent. This indicates clearly that the damping is caused by the superconductivity. The quantitative analysis is not successful because the magnetic field window is too small at 0.55 K Measurements at further low temperature using dilution' refrigerator is encouraged.Other K-type BEDT-TTF salts and BEDO-TTF salts are also investigated, however, no quantum oscillation effect was measured near the superconductivity transition region, at least down to 0.55 K.

有机超导体K1-（BEDT-TTEOsCuCNCS）2表现出由固有的层状结构增强的超导涨落效应。结果表明，超导转变是模糊的，没有明显的上临界场。为了深入了解超导转变特性，研究了量子振荡中出现的超导阻尼，并从超导涨落的角度分析了与布里斯托大学合作测量的de Haas-van Rezen效应中出现的超导阻尼因子。在0.5K以下，定量地阐明了超导能隙的涨落。它的角度依赖于外部磁场的方向表明的二维超导性和相关的涨落效应。为了研究正常状态下二维性的相关性，测量了电阻率各向异性的温度依赖性，测量了Shubnikovde哈斯效应，即电阻率的量子振荡，测量条件是在大气环境和2 kbar压力下，温度低至0.55 K，磁场高达9 T，由资助购买的磁体产生。在6.8 T以上观察到Shubnikovde哈斯效应。在6.8 ~ 7.3T的磁场范围内，振荡有附加阻尼，而在超导性被抑制的压力下，阻尼消失。这清楚地表明阻尼是由超导性引起的。由于磁场窗口在0.55K处太小，定量分析不成功，建议在更低的温度下用稀释制冷机进行测量，也研究了其他K型BEDT-TTF盐和BEDO-TTF盐，但在超导转变区附近，至少在0.55K以下，没有测量到量子振荡效应。