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

该材料世界网络项目旨在支持由一个国际研究小组在高强度加速器设施，如加拿大温哥华的TRIUMF和瑞士维利根的Paul Scherrer研究所（PSI）进行的μ子自旋弛豫（MuSR）测量的量子相变研究。 该团队包括来自哥伦比亚大学（美国）、麦克马斯特大学和TRIUMF（加拿大）、PSI（瑞士）、京都和东北大学（日本）、巴西物理研究中心（巴西CBPF）和巴里洛切原子中心（阿根廷CAB）的资深和初级科学家。 几十年来，相变的研究一直是通过改变温度（热相变）来进行的。 近年来材料和技术的发展为研究低温下相的量子演化开辟了新的途径。 QPT的许多新概念和未被探索的功能被揭示在重费米子系统，沮丧/低维磁体和奇异超导体的研究。 利用MuSR的独特能力，检测甚至非常小/随机磁矩的磁有序，估计涉及相分离的情况下磁有序区域的体积分数，并在非常宽的时间窗口内表征动态自旋波动，与其他技术互补，本项目将阐明受挫方形晶格J1-J2自旋系统中的磁QPT，掺杂磁性半导体（Ga，Mn）As和（Fe，Co）Si，新型氧化钌化合物，磁振子玻色凝聚的准一维自旋系统，以及UGe 2和其它重费米子系统。 材料开发领域领先研究人员的广泛合作（京都，东北），MuSR测量（哥伦比亚，McMaster），MuSR仪器（TRIUMF，PSI）、穆斯堡尔效应（CBPF）和重费米子物理（CAB），在世界上最强的介子设施（TRIUMF和PSI）与领先的理论家团队成员的密切参与（阿弗莱克，前川，米利斯），将推进对量子相界附近竞争态和软动力学模式的作用的基本理解。 这种进展可能有助于确定期待已久的新型超导体的机制，以及开发适用于自旋敏感晶体管的理想磁性半导体。来自所有参与机构的学生和博士后研究人员的参与为年轻科学家提供了宝贵的培训和国际研究经验，这些科学家在凝聚态物理学前沿研究的一个具有挑战性的领域。该项目使用了大型加速器设施和粒子物理学的原理。核物理学研究各种材料，包括新型超导体，以了解与磁性和量子物理学相关的特性，而这些特性是在这个研究领域的其他技术。一个国际研究小组将在位于不列颠哥伦比亚省温哥华的加拿大加速器设施TRIUMF进行他们测量的主要部分。该研究的重点是了解各种材料系统中的新凝聚态现象，包括表现出有趣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年轻科学家在这个项目中共同工作，并获得宝贵的国际研究经验。此外，还计划利用哥伦比亚大学现有的技术，为研究生和本科生开设网上课程和研讨会，并在所有参与机构之间交流。该奖项由材料研究部和数学与物理科学理事会多学科活动办公室以及国际科学与工程办公室共同资助。东亚和太平洋计划。

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.