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

该奖项支持西北大学的James A.Sauls教授与芬兰Abo学院的Juhani Kurkijarvi教授进行研究合作。他们正在对超流氦-3中的约瑟夫森效应进行理论研究，目的是了解弱连接中从耗散行为到非耗散超流的交叉。我们将计算约瑟夫森电流-相关系和超流氦-3中的弱连接所能支持的最大临界电流。这项工作应该为测量约瑟夫森效应的实验设计提供一个足够真实的超流体描述。这两位研究人员在超导准经典理论和准经典方程的数值解方面都有丰富的经验。库尔基亚维博士在超导约瑟夫森器件理论方面拥有特殊的专业知识，而索尔斯博士则是超流体性质方面的专家。作为一个团队，他们有突出的资格来完成拟议的工作，这应该会产生推进对量子效应物理理解所需的理论基础。重费米子金属中超导电性的发现引起了从事低温物理工作的理论家和实验学家的极大兴趣。对具有强空间变化的超导体的性质进行定量计算，例如弱连接和隧道结，是超导领域中最难解决的理论问题之一。这项合作研究将导致对超流氦-3中弱连接性质的定量计算，这将为连接非传统超导体的弱连接提供定性的见解，并导致基于约瑟夫森效应的更成功的器件。

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.