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A study on dynamical charge fluctuation and lattice dynamics of metal oxcides by X-ray inelastic scattering

X射线非弹性散射研究金属氧化物动态电荷涨落和晶格动力学

基本信息

批准号：
14340105
负责人：
YAMADA Kazuyoshi
金额：
$ 10.43万
依托单位：
Tohoku University (2003-2004)Kyoto University (2002)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The purpose of this project is to perform a systematic study on the interplay between dynamics of charge, spin and lattice in metal oxides with strongly correlated electrons.One experimental uniqueness of this project is a complementary use of both X-ray inelastic scattering and neutron scattering techniques. Another uniqueness is to use both large single crystals and concentration-graded crystals. Particularly, the latter crystals are firstly utilized to the comprehensive spectroscopic studies by X-ray inelastic scattering in this project. Theses experimental uniqueness contributed a lot to obtain the new results which are shown below.(I)In a wide doping region, we succeeded in growing concentration-graded crystals of Sr doped La_<2-x>Sr_xrCuO_4 with x extending from 0.00 to 0.30. By using a scanning SQUID magnetometer we also succeeded in observing a boundary between the semiconducting-superconducting phases in real space as a boundary of vortex states below the transition temperature.(II)By using a synchrotron X-ray beam with high luminosity and by emitting the beam spot onto the different positions on the concentration-graded crystal we could obtain the information of lattice dynamics as a function of doping concentration in a wide doping region for the first time. One of the important discoveries is the anomalous softening of the Cu-O bond stretching mode only seen in the superconducting region where the life-time of phonons is also anomalously short. These anomalies suggest the strong electron-phonon coupling in the superconducting doping region and provide us important information on the role of electron-phonon coupling in this system for the paring mechanism.

这个项目的目的是系统地研究具有强关联电子的金属氧化物中电荷、自旋和晶格动力学之间的相互作用。这个项目的一个实验独到之处是补充使用了X射线非弹性散射和中子散射技术。另一个独特之处是既可以使用大单晶，也可以使用浓度梯度晶体。特别是，在本项目中，后者首次被用于X射线非弹性散射的综合光谱研究。这些实验的独特性有助于得到如下新的结果：(1)在较宽的掺杂范围内，我们成功地生长出了浓度梯度的掺锶La_xLt；2-x&Gt；Sr_xrCuO_4晶体，x从0.00扩展到0.30。通过使用扫描SQUID磁强计，我们还成功地观测到了真实空间中半导体-超导相之间的边界作为低于转变温度的涡旋态的边界。(Ii)利用高亮度的同步加速器X射线束，通过将束斑发射到浓度梯度晶体上的不同位置，首次获得了宽掺杂区域内掺杂浓度随掺杂浓度变化的晶格动力学信息。其中一个重要发现是铜-氧键伸缩模式的反常软化，只有在超导区才能看到，那里的声子寿命也异常短。这些反常现象表明在超导掺杂区存在很强的电子-声子耦合，并为研究电子-声子耦合在该体系中的作用提供了重要的信息。