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质的固有的。 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以违反直觉，因此这激发了磁性的复杂性。人类对磁性的理解仍然缺乏对角动量保护的完整考虑。 1915年，爱因斯坦和德哈斯（EDH）进行了非常困难的（也是爱因斯坦的）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磁性扭矩，这会使指南针在其长轴周围旋转。不幸的是，少量的普通指南针扭矩也逐渐蔓延。他们的结果意外地同意了经典的预测，后来被认为是不正确的。我们的小组使用21世纪的纳米机器重新审视基础实验，例如EDH进行的基础实验。由于设备的振荡速度比1915年的设备快100,000倍，因此我们证明了违反直觉“ EDH”扭矩与普通指南针扭矩的比率也大100,000倍。在纳米版中，EDH扭矩可能是最强的扭矩！最重要的是，随着振荡频率继续增加，EDH扭矩不会获得强度。研究这种缩放如何分解将揭示有关如何使指南针转弯的机械扭矩实际上是从作用在针内的显微镜磁矩上的磁性扭矩的。这是自旋力学当代子场的重点。我们还将信号阶段，波峰的转移比对以及其他相似波形的槽中添加到测量方案中。相位可以产生重要的新信息，并且确实可以使爱因斯坦和德哈斯能够发现自己的错误，如果能力在其时间内可用。 此外，我们将将新的EDH方法应用于超导体，这是一类显示外来行为（例如磁悬浮）的量子材料。 EDH对超导性的研究仅在文献中仅3次报道，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了解，这可能有助于它们用作替代选择应用中稀有地球磁铁的替代品。拟议的研究基于过去赠款​​期的成就，其中包括与许多学生一起建立科学硬件制造商空间，或者用他们的话说：“棚屋，一个跨学科的创新，研究，研究和自我指导的学习”。该棚屋为大学生发现并为实验研究做出了贡献的机会，是招募和基础设施的完全有机部分。