Muon Studies of Quantum Materials and Novel States of Matter

量子材料包括广泛的科学迷人和技术重要的现象，包括高温超导性，非费米液体行为，巨磁阻，以及无数形式的磁性和铁电性。这些不寻常的行为似乎是由量子涨落引起的，量子涨落超出了相变，相变被非热控制参数（施加的压力，施加的磁场或电子密度的化学操纵）驱动到绝对零度（T = 0）。理解所谓的量子相变（QPT）和伴随的量子涌现现象是一个巨大的挑战，也是现代凝聚态物理学的中心目标。 QPT和相关的关键行为可以严重修改的障碍。无序可能是固有的，通过改变化学成分故意引入的，或由不同基态之间的密切竞争内在驱动的。在一般情况下，无序诱导的QPT预测驱动相关电子系统的新的量子无序相，而奇异的属性。 研究无序对量子临界现象的影响需要能够识别和表征量子临界区域中的无序或相分离的局部探测实验技术。在这方面，μ子自旋旋转/弛豫（SR）技术非常适合于提供其他方法无法实现的QPT的见解。当植入材料中时，正μ子（+）作为内部磁场的局部探针，允许测量磁性和超导特性。此外，SR具有独特的灵敏度的磁性区域的体积分数。 我计划把我的研究集中在量子材料的SR研究上，以提供非热控量子临界性的局部探测视角。我的方法将是利用加拿大新的SR实验能力，利用国外的设施，建立新的研究伙伴关系，以获得对各种强相关电子系统（例如，拓扑绝缘体、非常规超导体、新型磁阻金属）。 拟议的研究计划旨在确定在何种程度上相分离是一个普遍存在的现象的磁性QPT和阐明新的物质状态。所获得的知识将支持量子材料研究和技术，这是加拿大目前的战略优先研究领域。我的研究计划提供了一个肥沃的HQP培训基地，通过接触最先进的技术，参与尖端科学，广泛的合作以及旅行和传播研究成果的机会，提高学员的劳动力技能。

Quantum materials comprise a wide range of scientifically fascinating and technologically important phenomena, including high-temperature superconductivity, non-Fermi liquid behaviour, colossal magnetoresistance, and countless forms of magnetism and ferroelectricity. These unusual behaviours seemingly arise from quantum fluctuations extending beyond a phase transition that has been driven to absolute zero temperature (T = 0) by a non-thermal control parameter (applied pressure, applied magnetic field or chemical manipulation of electron density). Understanding so-called quantum phase transitions (QPTs) and the accompanying emergent quantum phenomena is a grand challenge and a central thrust of modern condensed matter physics. QPTs and associated critical behaviour can be severely modified by disorder. Disorder may be inherent, intentionally introduced by changing the chemical composition, or intrinsically driven by a close competition between different ground states. In general, disorder-induced QPTs are predicted to drive correlated-electron systems to novel quantum disordered phases with rather exotic properties. The investigation of the effects of disorder on quantum critical phenomena necessitates local-probe experimental techniques that are capable of recognizing and characterizing disorder or phase separation in the quantum critical region. The muon spin rotation/relaxation (SR) technique is well suited in this regard to provide insight on QPTs not attainable by other methods. When implanted in a material, the positive muon (+) serves as a local probe of internal magnetic field, allowing measurements of magnetic and superconducting properties. Moreover, SR has a unique sensitivity to volume fractions of magnetic regions. I plan to concentrate my research on SR investigations of quantum materials to provide a local probe's perspective on non-thermal controlled quantum criticality. My approach will be to exploit new SR experimental capabilities in Canada, utilize facilities abroad and forge new research partnerships to gain fundamental insight on quantum critical phenomena in a variety of strongly-correlated electron systems (e.g., topological insulators, unconventional superconductors, novel magnetically-frustrated metals). The proposed research initiatives aim to determine the extent to which phase separation is a ubiquitous phenomenon of magnetic QPTs and to elucidate novel states of matter. The knowledge gained will support quantum materials research and technology, which is a current strategic priority research area in Canada. My research plan provides a fertile HQP training ground for enhancing the workforce skills of trainees through exposure to state-of-the-art technologies, engagement in cutting-edge science, extensive collaborations, and opportunities to travel and disseminate research results.