EAGER: CRYO: Thermomagnetic Refrigeration

该项目由化学、生物工程、环境和运输系统部和材料研究部联合支持。许多关键物理现象和相只有在超低温、低于1K的情况下才能观察到。未来的基于量子的设备在量子计算、传感和通信中的应用依赖于超低温物理。因此，能够实现亚开尔文制冷的制冷技术的进步对于继续和扩大我们对基础和应用物理学的理解至关重要。目前广泛使用的实现亚开尔文的制冷技术是基于稀有氦同位素3He的使用。考虑到预计液氦的短缺和高昂的价格，开发能够实现未来可持续量子计算、传感和通信的替代技术至关重要。在可能的解决方案中，没有移动部件的固态技术很有吸引力，因为它们不需要维护。解决方案之一是Nernst-Ettinghausen制冷，这也是本提案的重点。除了全固态外，这些冰箱的设计极其简单，由单一材料制成。Nernst-Ettinghausen制冷是指当电场和磁场施加到固体材料(通常是半金属)上时，观察到由于热泵而沿着样品产生的温差。铋及其含锑合金在50K-150K温度范围内是一种有效的热磁材料。新发现的量子材料，即所谓的拓扑半金属，有可能将制冷工作温度延长到超低温。在PI Team初步开发的第一原理模型的基础上，该建议包括研究拓扑半金属的热磁性质，理论上没有合适的参数，并使用描述符和机器学习来识别用于亚开尔文制冷的新热磁材料。该提案设想了三项主要工作：(1)确定在1K以下的超低温下具有大优值系数的材料；(2)在2K-100K范围内对热磁性能进行实验表征；以及(3)建立并测试原理验证冰箱原型。该提议的学术价值在于对一大批新发现的材料进行了系统研究，这只有在计算方法方面的最新进步才有可能，包括该团队最近开发的基于第一原理的代码。建立和验证一套完整的理论-实验工具来评估材料的潜力，可以快速发现材料的独特性质。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project is jointly supported by the Division of Chemical, Bioengineering, Environmental and Transport Systems and the Division of Materials Research.Many critical physics phenomena and phases are only observable and occur at ultra-low temperatures, below 1K. Futuristic quantum-based devices for applications in quantum computing, sensing, and communications are dependent upon ultra-low temperature physics. Advances in refrigeration technologies enabling sub-Kelvin refrigeration are therefore crucial to continue and expand our understanding of fundamental and applied physics. The current widely used refrigeration technology to achieve sub-Kelvin is based on the usage of the rare helium isotope, 3He. Given the projected shortage and the high price of liquid helium, it is crucial to develop alternative technologies enabling future sustainable quantum computing, sensing, and communications. Among potential solutions, solid-state technologies with no moving parts are attractive since they do not require maintenance. One of the solutions, which is the focus of this proposal, is the Nernst-Ettingshausen refrigeration. In addition to being fully solid-state, these refrigerators have an extremely simple design and are made out of a single material. The Nernst-Ettingshausen refrigeration refers to the observation of a developed temperature difference along the sample as a result of heat pumping when an electric field and a magnetic field are applied to a solid material, usually a semi-metal. Bismuth and its alloys with antimony are shown to be efficient thermomagnetic materials in the 50K-150K temperature range. The newly discovered quantum materials, the so-called topological semimetals, have the potential of extending the refrigeration operating temperature to ultra-low temperatures. Based on PI team's primarily developed first-principles module, this proposal includes studying the thermomagnetic properties of topological semimetals, theoretically with no fitting parameters, and using descriptors and machine learning to identify new thermomagnetic materials for sub-Kelvin refrigeration. The proposal envisions three major thrusts: (1) Identify materials with a large figure of merit at ultra-low temperatures, below 1K, (2) Experimentally characterize the thermomagnetic properties in the 2K-100K range, and (3) Build and test a proof-of-principle refrigerator prototype. The intellectual merit of the proposal is in the systematic studying of a large group of newly discovered materials, which is only possible due to recent advances in computational methods, including the team's recently developed first-principle-based code. Building and validating a complete theoretical-experimental set of tools to evaluate the potential of materials enables a fast pace in the discovery of materials' unique properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.