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传统相变是由热波动驱动的，当其中一个相变温度被非相驱动至绝对零时，以竞争相为特征的强相关电子材料中可能会发生一种截然不同的转变。热控制参数（施加压力、施加磁场或电子密度的化学操作），在 QCP 附近可能会出现分隔物质的两个不同量子相的量子临界点（QCP）（例如高温）。超导性、非费米液体行为、磁性边缘的偏序）和量子涨落可以影响材料在高温下的性能。 理解量子临界性是现代凝聚态物理的一个巨大挑战，在许多情况下，量子临界点的发生可能会被在临界区域产生相分离的无序（外部或内部驱动）所规避。 μ 子自旋旋转/弛豫 (SR) 技术就是这样一种探针，该方法基于将自旋极化正 μ 子 (+) 植入材料中并随后检测衰变正电子。揭示局部磁场对μ子自旋运动的影响作为一种纯磁探针，SR方法对各种磁性都很敏感，并且对空间偏析相位敏感。 TRIUMF 分子与材料科学中心 (CMMS) 拥有一种独特的 SR 光谱仪，称为“NuTime”，它提供了一种探测强磁场下材料的方法，目前其在量子材料研究中的适用性有限。建议通过为 NuTime 配备 He-3 低温恒温器将材料冷却至亚开尔文温度，加拿大和国际研究人员可以将 SR 应用于量子临界性和新物质态的研究。拟议的设备将在西半球建立独特的量子材料研究能力，这是加拿大公认的战略优先研究领域。