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Summary of research on orbital orders and fluctuations

轨道序数和涨落研究综述

基本信息

批准号：
11220202
负责人：
KURAMOTO Yoshio
金额：
$ 15.23万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2002
项目状态：
已结题

项目摘要

This project has revealed new properties of matter due to orbital degrees of freedom by performing comprehensive study of systems ranging from 2p, 3d, to 4f and 5f electrons with "orbital order" and "orbital fluctuation" taken as key words. Furthermore, we have found new functionary materials by controlling the orbital degrees of freedom. In particular we mention the discovery of high-temperature superconductivity MgB2 and elucidation of its fundamental properties. The material has both sigma and pi orbitals which have very different properties. The coexistence influences essentially the physical property of MgB2. It has not been possible to grow large single crystals during the period of the project, but the project has paved the way for future development. On the other hand, we have reported a new high-temperature ferromagnet CaB2C2, and checked in detail the property of CaB6 and related materials. However, we have not yet excluded the possibility that Fe impurities may play an important role in realizing the ferromagnetism. For f electron systems, we have revealed characteristics of the orbital ordering in CeB6 and related materials, hidden order in URSu2Si2, and one-dimensional magnetism in Yb4As3, among other things.We organized every year domestic meetings open to general audience and a special meeting after the discovery of MgB2. In 2002 we organized an international conference in Sendai having about 150 participants and active discussions with high quality. The proceedings were published as supplement of the Physical Society of Japan.

本项目以“轨道顺序”和“轨道变动”为关键词，对2p、3d、4f、5f电子等系统进行综合研究，揭示了轨道自由度所带来的物质的新性质。此外，我们还通过控制轨道自由度发现了新的功能材料。特别是我们提到高温超导性MgB 2的发现和阐明其基本性质。该材料具有sigma和pi轨道，它们具有非常不同的性质。MgB2的物理性质主要受共存状态的影响。在项目期间还不可能生长大单晶，但该项目为未来的发展铺平了道路。另一方面，我们报道了一种新的高温铁磁体CaB_2C_2，并对CaB_6及其相关材料的性质进行了详细的考察。然而，我们还没有排除Fe杂质在实现铁磁性中可能起重要作用的可能性。对于f电子系统，我们揭示了CeB6及其相关材料的轨道有序、URSu2Si2中的隐藏有序和Yb4As3中的一维磁性等特征。我们每年组织一次国内公开会议，并在MgB2发现后组织一次专题会议。2002年，我们在仙台举办了一次国际会议，约有150人参加，并进行了高质量的积极讨论。该论文集作为日本物理学会的增刊出版。