Einstein-de Haas probes of equilibrium and nonequilibrium magnetism and superconductivity

爱因斯坦-德哈斯对平衡和非平衡磁性和超导性的探索

• 批准号: RGPIN-2021-02762
• 负责人: Freeman, Mark
• 金额: $ 3.64万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=742205
• 关键词: Einstein; de; Haas; probes; equilibrium

Embedded mechanical angular momentum is intrinsic to all things magnetic. Chudnovsky and Tejada describe a magnetic solid as a huge number of interacting quantum gyroscopes. Since even classical gyroscopes can behave counter-intuitively, this motivates the complexity of magnetism. Humanity's understanding of magnetism still lacks a complete accounting of angular momentum conservation. In 1915, Einstein and de Haas (EdH) performed a very difficult (and Einstein's only) experiment to measure the ratio of angular momentum to magnetic moment in iron. They observed for the first time a tiny, additional magnetic torque that would make a compass needle rotate about its long axis. Unfortunately, a tiny amount of ordinary compass needle torque also crept in. Their result accidentally agreed with a classical prediction, later understood to be incorrect. Our group uses 21st-century nanomachines to revisit foundational experiments such as the one performed by EdH. With devices oscillating 100,000 times faster than those used in 1915, we demonstrated that the ratio of the counter-intuitive "EdH" torque to ordinary compass torque is also 100,000 times larger. In nanodevices, the EdH torque can be the strongest one! Best of all, the EdH torque will not gain strength without limit as oscillation frequencies continue to increase. Studying how this scaling breaks down will reveal fundamentally new information about how the mechanical torque that makes a compass needle turn actually follows from the magnetic torques acting on the microscopic magnetic moments inside the needle. This is a focus of the contemporary sub-field of spin mechanics. We also add signal phase, the shifting alignment of crests and troughs of otherwise similar waveforms, to the measurement protocol. Phase yields important new information, and indeed could have enabled Einstein and de Haas to spot their error, had the capability been available in their time. Additionally, we will apply the new EdH methods to superconductors, a class of quantum materials that displays exotic behaviour such as magnetic levitation. EdH studies of superconductivity have been reported in the literature only three times, most recently in 1958. Modern EdH experiments will extend our knowledge of how superconductors interact with magnetic field, possibly contributing to their use as replacements for rare-earth permanent magnets in select applications. The proposed research builds on accomplishments from the past grant period, which included working together with many students to establish a Science Hardware Makerspace, or in their words: "The Shack, an interdisciplinary workshop for innovation, research, and self-directed learning". The Shack expands opportunities for undergraduates to discover and contribute to experimental research, and is a fully organic part of recruiting and infrastructure for the work proposed.

嵌入的机械角动量是所有磁性物体的固有特性。Chudnovsky和Tejada将磁性固体描述为大量相互作用的量子陀螺仪。由于即使是经典的陀螺仪也可能表现出与直觉相反的行为，这激发了磁学的复杂性。人类对磁性的理解仍然缺乏对角动量守恒的完整解释。1915年，爱因斯坦和德哈斯（EdH）进行了一个非常困难的（也是爱因斯坦唯一的）实验，测量铁的角动量与磁矩的比值。他们第一次观察到一个微小的额外的磁力矩，它会使指南针绕着它的长轴旋转。不幸的是，一个普通的指南针指针扭矩的微小数额也悄悄。他们的结果意外地与一个经典的预测一致，后来被认为是不正确的。我们的团队使用21世纪的纳米机器来重新审视基础实验，例如EdH进行的实验。随着设备的振荡速度比1915年使用的设备快100，000倍，我们证明了反直觉的“EdH”扭矩与普通指南针扭矩的比率也大100，000倍。在纳米器件中，EdH扭矩可以是最强的一个！最重要的是，随着振荡频率的不断增加，EdH扭矩不会无限制地获得强度。研究这种比例如何分解，将从根本上揭示新的信息，即使指南针指针转动的机械扭矩实际上是如何遵循作用于指针内部微观磁矩的磁矩的。这是当代自旋力学子领域的一个焦点。我们还增加了信号相位，波峰和波谷的移位对齐，否则类似的波形，测量协议。相位产生了重要的新信息，如果当时有这种能力的话，确实可以让爱因斯坦和德哈斯发现他们的错误。 此外，我们将把新的EdH方法应用于超导体，这是一类量子材料，显示出奇异的行为，如磁悬浮。EdH对超导性的研究在文献中只报道过三次，最近一次是在1958年。现代EdH实验将扩展我们对超导体如何与磁场相互作用的知识，可能有助于它们在某些应用中作为稀土永磁体的替代品。拟议的研究建立在过去资助期的成就基础上，其中包括与许多学生合作建立科学硬件制造商空间，或者用他们的话说：“The Shack，一个创新，研究和自主学习的跨学科研讨会”。该棚屋扩大了本科生发现和促进实验研究的机会，是招聘和基础设施的工作提出的一个完全有机的一部分。