Materials World Network: Studies of Quantum Phase Transitions by MuSR in Ambient and Applied Pressure

材料世界网络：MuSR 在环境压力和外加压力下研究量子相变

• 批准号: 0806846
• 负责人: Yasutomo Uemura
• 金额: $ 52.5万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0806846&HistoricalAwards=false
• 关键词: Materials; World; Network; Studies; Quantum

This Materials-World-Network project aims to support studies of quantum phase transitions (QPTs) by the muon spin relaxation (MuSR) measurements to be performed at high-intensity accelerator facilities, such as TRIUMF in Vancouver, Canada and Paul Scherrer Institut (PSI) in Villigen, Switzerland, by an international team of researchers. The team includes senior and junior scientists from Columbia University (USA), McMaster University and TRIUMF (Canada), PSI (Switzerland), Kyoto and Tohoku Universities (Japan), Brazilian Center for Research in Physics (CBPF, Brazil) and Centro Atomico Bariloche (CAB, Argentina). For many decades, studies of phase transitions have been performed exclusively by varying temperatures (thermal phase transitions). Recent developments of materials and technologies have opened a new window to investigate quantum evolutions of phases at low temperatures by varying pressure or composition as a tuning parameter. Many novel concepts and unexplored features of QPTs are being revealed in studies of heavy-fermion systems, frustrated / low-dimensional magnets and exotic superconductors. Taking advantage of unique capability of MuSR to detect magnetic order of even very small / random magnetic moments, to estimate volume fraction of magnetically ordered regions in a situation involving phase separation, and to characterize dynamic spin fluctuations in a very wide time window complementary to other techniques, the present project will elucidate magnetic QPT's in frustrated square-lattice J1-J2 spin systems, doped magnetic semiconductors (Ga,Mn)As and (Fe,Co)Si, novel ruthenium oxide compounds, quasi one-dimensional spin system which exhibits Bose Condensation of magnons, as well as UGe2 and other heavy-fermion systems. Extensive collaboration of leading researchers in materials development (Kyoto, Tohoku), MuSR measurements (Columbia, McMaster), MuSR instrumentation (TRIUMF, PSI), Moessbauer effect (CBPF), and heavy-fermion physics (CAB), at the world's strongest meson facilities (TRIUMF and PSI) with close involvement of leading theorist team members (Affleck, Maekawa, Millis), will advance basic understandings of the role of competing states and soft dynamic modes near quantum phase boundaries. Such progress could contribute to long-awaited determination of mechanisms for novel superconductors as well as to development of ideal magnetic semiconductors suitable for application to spin-sensitive transistors. Involvement of students and postdoctoral researchers from all participating institutions provides valuable training and international research experience to young scientists in a challenging area of cutting-edge research in condensed matter physics.This project uses large accelerator facilities and principles from particle/nuclear physics to study a variety of materials including novel superconductors to understand properties related to magnetism and quantum physics not accessible to other techniques in this research area. An international team of researchers will conduct the main part of their measurements at TRIUMF, a Canadian accelerator facility in Vancouver, British Columbia. The research is focused on understanding novel condensed matter phenomena in a variety of materials systems including semiconductors and oxide compounds that exhibit interesting magnetic behavior. Students and junior scientists from the US, Canada, Brazil, Argentina, Switzerland and Japan work together in this project and gain valuable international research experience. In addition, web-based courses and seminars for graduate, undergraduate students are planned to be developed and shared among all participating institutions using the technology already available at Columbia University. This award is jointly funded by the Division of Materials Research and the Office of Multidisciplinary Activities in the Mathematical and Physical Sciences Directorate and by the Office of International Science and Engineering ?East Asia and pacific Program.

此材料世界网络项目旨在通过在高强度加速器设施上进行的MUON自旋松弛（MUSR）测量来支持对量子相变（QPTS）的研究，例如，加拿大温哥华的Triumf和国际瑞士的Paul Scherrer Institut（PSI），由国际研究员组成的瑞士。 该小组包括来自哥伦比亚大学（美国），麦克马斯特大学和弗里姆夫（加拿大），PSI（瑞士），京都和东北大学（日本），巴西物理学研究中心（CBPF，巴西）和Centro Atro Atro Atomicoico Bariloche（Cab，Argentina）的小组。 数十年来，对相变的研究仅通过不同的温度（热相变）进行。 材料和技术的最新发展已经为在低温下通过变化的压力或组成作为调谐参数在低温下研究相的量子演变开了一个新窗口。 在重点系统，沮丧 /低维磁铁和异国情调的超导体的研究中揭示了许多QPT的新颖概念和未开发的特征。 Taking advantage of unique capability of MuSR to detect magnetic order of even very small / random magnetic moments, to estimate volume fraction of magnetically ordered regions in a situation involving phase separation, and to characterize dynamic spin fluctuations in a very wide time window complementary to other techniques, the present project will elucidate magnetic QPT's in frustrated square-lattice J1-J2 spin systems, doped magnetic semiconductors (Ga,Mn)As and （FE，CO）SI，新型氧化钌化合物，准一维自旋系统，该系统表现出镁的Bose凝结，以及UGE2和其他重毛皮系统。 材料开发领先研究人员（京都，东北），MUSR测量（哥伦比亚，麦克马斯特），MUSR仪器（Triumf，PSI），Moessbauer效应（CBPF）和重型效果物理学（CAB）的广泛合作，在世界上最强大的Meson设施（Triumf和PSI）（Triumf和PSI）（Triumf和PSI）（Triumf和PSI）（领先的Maek）（FARNA） MILLIS），将提高人们对竞争状态和量子相边界附近软动态模式的作用的基本理解。 这种进步可能有助于期待已久的新型超导体机制，以及适合于自旋敏感晶体管应用的理想磁性半导体的发展。来自所有参与机构的学生和博士后研究人员的参与为凝聚态物理学的尖端研究的挑战领域提供了宝贵的培训和国际研究经验。本项目使用粒子/核物理学的大加速器设施和原理来研究与其他相关的多种材料，以了解与其他技术相关的各种材料，而不是访问其他技术，这些材料与其他技术相关。国际研究人员团队将在不列颠哥伦比亚省温哥华的加拿大加速器设施Triumf进行测量的主要部分。这项研究的重点是理解各种材料系统中新型凝结物质现象，包括表现出有趣的磁性行为的半导体和氧化物化合物。 来自美国，加拿大，巴西，阿根廷，瑞士和日本的学生和初级科学家在这个项目中共同努力，并获得宝贵的国际研究经验。此外，计划使用哥伦比亚大学已经可用的技术在所有参与机构中开发和共享基于Web的课程和研究生，本科生。该奖项由材料研究部以及数学和物理科学局的多学科活动办公室以及国际科学与工程学办公室共同资助。东亚和太平洋计划。