U.S.-Finland Cooperative Research: Theory of Josephson Effects in Superfluid Helium-3

该奖项支持美国西北大学的James a . Sauls教授与芬兰阿博研究院的Juhani Kurkijarvi教授合作开展的一项研究。他们正在对超流体氦-3中的约瑟夫森效应进行理论研究，目的是理解弱环节中从耗散行为到非耗散超流的交叉。将计算约瑟夫森电流-相关系和超流体氦-3中的弱链所能支持的最大临界电流。这项工作应该提供一个足够真实的超流体描述，为设计测量约瑟夫森效应的实验提供有价值的指导。两位研究者在超导的准经典理论和准经典方程的数值解方面都有丰富的经验。库尔基雅尔维博士在超导约瑟夫森装置理论方面有特别的专长，而索尔斯博士是超流体特性方面的专家。作为一个团队，他们在提议的工作中具有出色的资格，这应该为推进对量子效应物理学的理解提供必要的理论基础。重费米子金属超导性的发现引起了从事低温物理工作的理论家和实验家的极大兴趣。具有强空间变异性的超导体（如弱连接和隧道结）性质的定量计算是超导领域最难解决的理论问题之一。这项合作研究将对超流体氦-3中弱链接的性质进行定量计算，这将为连接非常规超导体的弱链接提供定性的见解，并导致基于约瑟夫森效应的更成功的设备。

This award supports Professor James A. Sauls of Northwestern University in a research collaboration with Professor Juhani Kurkijarvi of the Abo Academy, Abo, Finland. They are carrying out a theoretical study of the Josephson effect in superfluid helium-3, with the goal of understanding the crossover from dissipative behavior to non-dissipative superflow in weak links. Calculations will be done of the Josephson current-phase relation and the maximum critical current that can be supported by a weak link in superfluid helium-3. This work should provide a sufficiently realistic description of the superfluid to be a valuable guideline for the design of experiments to measure the Josephson effect. Both investigators have substantial experience in the quasiclassical theory of superconductivity and in numerical solutions of the quasiclassical equations. Dr. Kurkijarvi has particular expertise in the theory of superconducting Josephson devices, while Dr. Sauls is an expert on the properties of superfluids. As a team they have outstanding qualifications for the proposed work, which should produce the theoretical basis needed to advance understanding of the physics of quantum effects. The discovery of superconductivity in the heavy fermion metals has generated considerable interest from theorists and experimentalists working in low temperature physics. Quantitative calculations of the properties of superconductors with strong spatial variations, e.g., weak links and tunnel junctions, are among the hardest theoretical problems to solve in the field of superconductivity. The quantitative calculations of the properties of weak links in superfluid helium-3 that will result from this collaborative research should provide qualitative insights into weak links connecting unconventional superconductors and lead to more successful devices based upon the Josephson effect.