Muon Studies of Quantum Materials and Novel States of Matter

量子材料包含了广泛的科学上迷人的和技术上重要的现象，包括高温超导，非费米液体行为，巨大的磁电阻，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超越相变的量子波动引起的，相变是由非热控制参数（施加压力、施加磁场或对电子密度的化学操纵）驱动到绝对零度（T = 0）的。理解所谓的量子相变（QPTs）和伴随的涌现量子现象是一个巨大的挑战，也是现代凝聚态物理的中心推动力。*** qpt和相关的关键行为可因紊乱而严重改变。无序可能是固有的，通过改变化学成分有意引入的，也可能是由不同基态之间的密切竞争内在驱动的。一般来说，无序诱导的量子点被预测将驱动相关电子系统到具有相当奇特性质的新型量子无序相。***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的无序或相分离的局部探针实验技术。在这方面，μ子自旋/弛豫（SR）技术非常适合提供其他方法无法实现的qpt的见解。当植入材料时，正μ子（+）充当内部磁场的局部探针，允许测量磁性和超导特性。此外，SR对磁性区域的体积分数具有独特的敏感性。***我计划将我的研究集中在量子材料的SR研究上，为非热控量子临界性提供一个局部探针的视角。我的方法将是在加拿大开发新的SR实验能力，利用国外的设施并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，新型磁性受挫金属）中的量子临界现象的基本见解。***提出的研究计划旨在确定相分离在多大程度上是磁性qpt的普遍现象，并阐明物质的新状态。所获得的知识将支持量子材料的研究和技术，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培训场地，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，来提高受训者的劳动力技能。

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.