Inter-American Materials Collaboration (CIAM): Probing Quantum Phase Transitions by MuSR and Complementary Methods in Applied Pressure

这一美洲材料合作(CIAM)项目旨在研究相关电子系统的量子相变和量子临界行为，方法是开发一台用于高压测量的新光谱仪，并在温哥华TRIUMF(温哥华)进行合作的Muon自旋弛豫(MSR)实验，同时对输运(多伦多)、磁化(肯塔基)、Moessbauer和微扰角关联(PAC)(CBPF-巴西)进行补充研究。与其他微观方法(中子散射和核磁共振)相比，MSR在测量(1)磁序区的体积分数；(2)磁序度；(3)超导系统中磁场穿透深度的绝对值方面有很大的优势。凭借这些独特的能力，这个项目将阐明：(A)在MnSi和ZrZn2中从巡回电子铁磁性到相关顺磁的交叉；(B)CeCu2Si2中磁性和超导电性的相互作用；(C)URu2Si2中“隐藏有序”和反铁磁态之间的竞争；(D)金属间Ce化合物的磁有序体系；以及(E)Ca2RuO4中压力诱导的Mott转变。该项目还将促进来自美国、加拿大、巴西和阿根廷的有经验的和年轻的科学家参与广泛的国际合作，其中包括来自代表性不足群体的几名科学家。这项拟议的工作将在温哥华、肯塔基州和里约热内卢的独特设施中进行，同时丰富哥伦比亚大学、肯塔基大学以及加拿大、巴西和阿根廷其他参与机构的研究生和本科生教学资源。Muon自旋弛豫(MSR)、Moessbauer效应和微扰角关联(PAC)是基于粒子/核物理的技术和原理应用于固体物理中的磁性和超导研究的强大方法。目前的项目是由来自美国、加拿大、巴西和阿根廷的科学家和学生共同合作的美洲材料合作(CIAM)。来自哥伦比亚大学和肯塔基大学的一组研究人员将开发在高压下测量MSR信号的能力，并使用位于温哥华的加拿大加速器设施TRIUMF进行MSR实验。该项目还涉及巴西CBPF-Rio的Moessbauer和PAC测量，以及阿根廷、多伦多、纽约和肯塔基州的其他补充研究。这些技术将被应用于现代固体物理的主题。目标是了解材料系统所表现出的新现象，在这些新现象中，强电子关联在决定超导和磁性方面发挥着主要作用。该项目将支持来自美国、加拿大、巴西和阿根廷的高级、初级科学家和学生，包括几名来自代表性不足群体的科学家，同时丰富相关机构的研究生和本科生教学资源。

This Inter-American Materials Collaboration (CIAM) project aims to study quantum phase transitions and quantum critical behaviors of correlated electron systems by developing a new spectrometer for high-pressure measurements and performing collaborative muon spin relaxation (mSR) experiments at TRIUMF (Vancouver), together with complementary studies of transport (Toronto), magnetization (Kentucky), and Moessbauer and Perturbed Angular Correlation (PAC) (CBPF-Brazil). mSR has advantages over other microscopic methods (neutron scattering and NMR), in measurements of (1) volume fraction of magnetically ordered regions; (2) magnetic orderof very small / random / dilute moments; and (3) the absolute values of the magnetic field penetration depth in superconducting systems. With these unique capabilities, this project would elucidate: (a) the crossover from itinerant electron ferromagnetism to correlated paramagnetism in MnSi and ZrZn2; (b) interplay of magnetism and superconductivity in CeCu2Si2; (c) competition between the "hidden order" and antiferromagnetic states in URu2Si2; (d) magnetic-ordering systematics of intermetallic Ce compounds; and (e) pressure-induced Mott transition in Ca2RuO4. This project would also promote the participation of experienced as well as young scientists from the US, Canada, Brazil, and Argentina, including several scientists from under-represented groups, in extensive international collaboration. The proposed work will be performed at unique facilities in Vancouver, Kentucky, and Rio de Janeiro, while enriching graduate and undergraduate teaching resources of Columbia Univesity, University of Kentucky, and other participating institutions in Canada, Brazil, and Argentina.Muon Spin Relaxation (mSR), Moessbauer effect, and Perturbed Angular Correlations (PAC) are powerful methods based on technologies and principles from particle/nuclear physics applied to the study of magnetism and superconductivity in solid state physics. The present project is an Inter-American Materials Collaboration (CIAM) in which scientists and students from the US, Canada, Brazil, and Argentina work together. A team of researchers from Columbia University and University of Kentucky will develop capabilities for measuring mSR signals at high applied pressure and perform mSR experiments using TRIUMF, a Canadian accelerator facility in Vancouver. The project also involves Moessbauer and PAC measurements at CBPF-Rio in Brazil, and other complementary studies in Argentina, Toronto, New York, and Kentucky. These techniques will be applied to topical subjects of modern solid-state physics. The goal is to understand novel phenomena exhibited by materials systems in which strong electron correlations play a major role in determining the superconducting and magnetic properties. This project will support senior, junior scientists and students from the US, Canada, Brazil, and Argentina, including several scientists from under-represented groups, while enriching graduate and undergraduate teaching resources of the involved institutions.