He-3 Cryostat for Muon Spin Rotation/Relaxation Studies of Quantum Materials

用于量子材料 Mu 子自旋旋转/弛豫研究的 He-3 低温恒温器

• 批准号: RTI-2017-00478
• 负责人: Luke, Graeme
• 金额: $ 10.93万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=616686
• 关键词: He; Cryostat; Muon; Spin; Rotation

Conventional phase transitions between an ordered and disordered state are driven by thermal fluctuations. A profoundly different kind of transition can occur in strongly-correlated electronic materials characterized by competing phases. When one of the phase transition temperatures is driven to absolute zero by a non-thermal control parameter (applied pressure, applied magnetic field or chemical manipulation of electron density), a quantum critical point (QCP) separating two distinct quantum phases of matter may occur. Near a QCP unusual phenomena can emerge (e.g. high-temperature superconductivity, non-Fermi liquid behaviour, partial order at the verge of magnetism) and quantum fluctuations can affect the properties of a material to remarkably high temperatures. Understanding quantum criticality constitutes a grand challenge of modern condensed matter physics. In many cases the occurrence of a QCP may be circumvented by disorder (extrinsically or intrinsically driven) that produces phase separation in the critical region. Local experimental probes are required to recognize and characterize phase separation. The muon spin rotation/relaxation (SR) technique is such a probe. This method is based on the implantation of spin-polarized positive muons (+) in a material and the subsequent detection of the decay positrons to reveal the influence of the local magnetic fields on the motion of the muon spin. As a pure magnetic probe, the SR method is sensitive to various kinds of magnetism and is sensitive to spatially segregated phases. The Centre for Molecular and Materials Science (CMMS) at TRIUMF is home to a unique SR spectrometer, called “NuTime”, which provides a means of probing materials subject to a high magnetic field. Its applicability to the study of quantum materials is currently limited by temperature. It is proposed, that by outfitting NuTime with a He-3 cryostat to cool materials to sub-Kelvin temperatures, Canadian and International researchers can apply SR to the study of quantum criticality and novel states of matter tunable by applying magnetic field. The proposed equipment will establish a unique capability in the Western Hemisphere for quantum materials’ research, a recognized strategic priority research area in Canada.

有序状态和无序状态之间的常规相变是由热波动驱动的。在以竞争阶段为特征的强相关电子材料中，可能发生完全不同的过渡。当一个非热控制参数（施加的压力，施加的磁场或电子密度的化学操作）将相变温度之一驱动到绝对零时，可能会出现量子临界点（QCP），将物质的两个不同的量子相分开。在QCP附近，异常现象会出现（例如，高温超导性，非纤维液体行为，磁性的部分阶阶，量子波动）和量子波动可能会影响材料的性质至明显高的温度。 理解量子批判性构成了现代冷凝物理物理学的巨大挑战。在许多情况下，QCP的发生可能会通过在关键区域产生相位分离的疾病（外部或本质上驱动）的疾病（外部或本质上驱动）。需要局部实验问题才能识别和表征相位分离。 MUON自旋旋转/松弛（SR）技术就是这样的探针。该方法基于在材料中植入自旋偏振正阳性的（+）的植入，以及随后检测到衰减阳性的检测，以揭示局部磁场对MUON旋转运动的影响。作为纯磁探针，SR方法对各种磁性敏感，并且对空间隔离相敏感。 Triumf的分子和材料科学中心（CMM）是独特的SR光谱仪的所在地，称为“ Nutime”，它提供了一种探测材料的手段。有人提出，通过将Nutime与HE-3低温恒温器一起拟合到凯文温度的冷却材料中，加拿大和国际研究人员可以通过应用磁场将SR应用于量子关键性和物质可调节的新型状态的研究。拟议的设备将在西半球建立独特的能力，以进行量子材料研究，这是加拿大公认的战略优先研究领域。