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。丘德诺夫斯基和特贾达将磁性固体描述为大量相互作用的量子陀螺仪。由于即使是经典陀螺仪的行为也可能与直觉相反，这就增加了磁学的复杂性。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)进行了一项非常困难(也是爱因斯坦唯一的)的实验，以测量铁中角动量与磁矩的比率。他们首次观察到一个微小的附加磁力矩，可以使指南针绕其长轴旋转。不幸的是，普通的指南针扭矩也悄悄出现了。他们的结果意外地与一个经典预测吻合，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，比如由EDH进行的实验。由于设备的摆动速度比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是100,000倍。在纳米器件中，EDH扭矩可能是最强的！最好的是，随着振荡频率的不断增加，EDH扭矩不会无限增加强度。研究这种比例是如何分解的，将从根本上揭示使指南针转动的机械扭矩实际上是如何跟随作用于指南针内部微观磁矩的磁力矩的。这是自旋力学当代子领域的一个焦点。我们还在测量协议中增加了信号相位，即其他类似波形的波峰和波谷的移位对齐。阶段产生了重要的新信息，确实可以让爱因斯坦和德哈斯发现他们的错误，如果他们那个时代有这种能力的话。此外，我们将把新的EDH方法应用于超导体，这是一类显示出磁悬浮等奇异行为的量子材料。EDH对超导电性的研究在文献中只被报道过三次，最近一次是在1958年。现代EDH实验将扩展我们对超导体与磁场相互作用的知识，可能有助于在某些应用中替代稀土永磁体。这项拟议的研究建立在过去拨款期间取得的成就的基础上，其中包括与许多学生合作建立一个科学硬件制造空间，或者用他们的话说：“Shack，一个创新、研究和自我指导学习的跨学科研讨会”。棚屋为本科生扩大了发现和贡献实验研究的机会，是拟议工作的招聘和基础设施的完全有机的一部分。