MuSR Studies of Exotic Spin and Charge Behaviors in Novel Superconductors, Metals, and Semiconductors

****技术摘要**** μ子自旋弛豫（MuSR）测量为磁有序研究提供了关于有序体积分数、矩大小、慢自旋波动和临界行为的独特信息，并允许可靠地确定ii型超导体中的超流体密度。本项目旨在通过在TRIUMF（加拿大）和PSI（瑞士）进行广泛的MuSR测量，研究新型超导和磁性系统中的奇异自旋和电荷相关性。目前的研究包括：(1)弱流动铁/螺旋磁体MnSi和FeGe中的量子临界行为和Skyrmion自旋相关性，(2)在I-II-V半导体LiZnAs中掺杂电荷（过量Li）和自旋（带Mn）产生的新型铁磁系统Li(Zn,Mn)，以及(3)各种FeAs， CuO和重费米子超导体，特别关注过掺杂区域的奇怪/无法解释的行为。本项目的成功将促进对在许多这些系统中发现的非常强的和非常规的自旋电荷耦合的理解，并可能有助于开发新的超导和自旋电子学系统和设备。MuSR测量将在广泛的国际合作中进行，在独特的多国环境和设施中为研究生、本科生和博士后学生和研究人员提供发展机会。拓展计划包括开发在线讲座课程，以及让高中生参与其中。****非技术摘要****在过去的30年里，随着许多新颖和非常规材料和现象的发现，固体物理学得到了发展。它们包括高tc CuO超导体，掺杂铁磁半导体，以及存在于磁性有序和无序（或超导）状态边界的系统。这些系统的关键要素是自旋（磁性的起源）和电荷（金属、半导体或超导行为所必需的）之间的强相互作用。现代固体物理学的另一个显著发展是使用大型加速器设备，产生高强度的x射线、中子和介子束。目前的项目将使用在加拿大（TRIUMF）和瑞士（PSI）的专用高强度加速器设施中获得的正介子来阐明磁性（自旋）和导电（电荷）现象之间的详细关系。研究进展可能有助于开发超导和/或自旋敏感电子（自旋电子学）器件的新材料。μ子测量将在国际合作中进行，包括来自美国、加拿大、日本、中国、巴西、英国和瑞士的团队，这将有助于学生和研究人员在独特的多国环境中发展。教育/拓展活动包括固态物理在线讲座课程的开发，与教科书和实验课程相关联。通过与TRIUMF的外展活动合作，该项目支持高中生和物理教师参与使用大型加速器设施的前沿实验研究。

****Technical Abstract****Muon spin relaxation (MuSR) measurements provide unique information on the ordered volume fraction, moment size, slow spin fluctuations, and critical behavior for studies of magnetic ordering, and allow reliable determination of the superfluid density in type-II superconductors. The present project aims to study exotic spin and charge correlations in novel superconducting and magnetic systems by extensive MuSR measurements at TRIUMF (Canada) and PSI (Switzerland). The present research covers: (1) quantum critical behaviors and Skyrmion spin correlations in weak itinerant ferro/helical magnets MnSi and FeGe, (2) novel ferromagnetic system Li(Zn,Mn)As generated by doping charge (with excess Li) and spin (with Mn) into the I-II-V semiconductor LiZnAs, and (3) various FeAs, CuO and heavy fermion superconductors, with a special focus on strange/unexplained behaviors in the overdoped regions. Success of the present project will advance understanding of very strong and unconventional spin-charge couplings found in many of these systems, and possibly contribute to development of new superconducting and spin-tronics systems and devices. The MuSR measurements will be performed in extensive international collaborations, providing opportunities for development of graduate, undergraduate and post-doctoral students and researchers in a unique multi-national environment and facilities. Outreach plans include development of on-line lecture courses, and involvement of high school students.****Non Technical Abstract****Over the last 30 years, solid state physics has developed with discoveries of many novel and unconventional materials and phenomena. They include high-Tc CuO superconductors, doped ferromagnetic semiconductors, and systems existing in the boundary of magnetically ordered and disordered (or suprconducting) states. The key element of these systems is strong interaction between spins (origin of magnetism) and charges (required for metallic, semiconducting, or superconducting behaviors). Another notable development of modern solid state physics is the use of large accelerator facilities which produce high-intensity beams of X-rays, neutrons and muons. The present project will use positive muons obtained at dedicated high-intensity accelerator facilities in Canada (TRIUMF) and Switzerland (PSI) to elucidate detailed relationship between magnetic (spin) and conductive (charge) phenomena. Rsearch advances may contribute to development of novel materials for superconducting and / or spin-sensitive electronics (spintronics) devices. The muon measurements will be performed in international collaboration including gropus from the US, Canada, Japan, China, Brazil, UK and Switzerland, which will help development of students and researchers in a unique multi-national environment. Educational/outreach activities include the development of on-line lecture courses for solid state physics, associated with text books and lab courses. In cooperation with TRIUMF's outreach activities, the project supports involvements of high school students and physics teachers in forefront experimental research using very large accelerator facilities.