状交C60的结构及其对超导特性的影响
Robert E Dinnebier1, Olle Gunnarsson, Holger Brumm
1Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Science (New York, N.Y.)
|April 6, 2002
概括
富勒烯化合物如C60.CHCl3和C60.CHBr3的超导率达到117K.结构分析显示了晶格膨胀,但带结构计算表明,仅此并不能解释高过渡温度.
科学领域:
- 材料科学 材料科学 材料科学
- 凝聚物质物理学 凝聚物质物理学
- 固态化学 固态化学
背景情况:
- 富勒烯化合物,特别是C60与CHCl3和CHBr3相间隙,表现出高超导过渡温度 (Tc).
- 这些材料中先前发现的高达117K的Tc引起了大量的科学兴趣.
- 了解控制这种超导性的结构和电子因素对于材料开发至关重要.
研究的目的:
- 通过使用先进的衍射技术来确定CHCl3和CHBr3间隔C60的晶体结构.
- 在费米水平上研究电子带结构和状态密度.
- 阐明结构修改,电子性质和观察到的高超导过渡温度之间的关系.
主要方法:
- 采用同步射线X射线粉末衍射技术,精确确定晶体结构.
- 进行了紧密结合带结构计算,用于插入的富勒烯的表面层.
- 分析侧重于格子扩张,分子排列和费米能量状态的电子密度.
主要成果:
- 晶体结构显示出显著的格子扩张,主要沿着三临床b轴.
- C60分子在结构中形成一个大约六角形,稍微扩展的格子.
- 带结构计算表明,与原始C60相比,C60.2CHCl3和C60.2CHBr3的费米能量状态密度较低,特别是在与高Tc相关的兴奋剂中.
结论:
- 在CHCl3和CHBr3间隔的C60中,晶格膨胀发生在异型态上.
- 观察到的高超导过渡温度不能仅仅归因于晶格膨胀.
- 电子因素,如费米级状态的密度,起着至关重要的作用,需要进一步的研究,以充分解释增强的超导.
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