EAGER: CRYO: Thermomagnetic Refrigeration

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

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.