****Technical Abstract**** A newly developed technique of three-tone intermodulation distortion will be used to examine the nonlinear electrodynamics of high-temperature superconducting (HTS) thin films in the microwave frequency regime. This method generates multiple orders of nonlinearity at the same frequency, thereby eliminating time-scale and dispersion differences between the different orders. Using this advantage, the physical origin of even and odd order nonlinearity will be probed in patterned HTS passive microwave devices. The contribution of patterning to nonlinearity, in particular to time reversal symmetry breaking, will be determined by comparing devices comprised of sloped or vertical line edges. The contribution of crystalline symmetry will be understood by comparing devices made from yttrium and thallium based HTS materials. Finally, the contribution of hole doping will be understood by modifying films with nitrogen gas anneals. The bulk of this work will be done by a team of six to ten undergraduates pursuing degrees in physics and engineering. Along with learning in-demand skills such as microwave test and measurement and finite element analysis, students will learn to be effective researchers by developing experiment plans, presenting at conferences and contributing to publications in the peer reviewed literature.
High temperature superconductors were discovered in the 1980's and since then there has been a variety of commercial applications. One application area of both commercial and military value is in high frequency electronics where the absence of resistance permits device performance far beyond that seen conventionally. A limit to high frequency device applications of superconductors results from the tendency of superconductors to distort the electronic signals. This research seeks an understanding of this distortion at a fundamental physics level by studying how the superconductors violate time reversal symmetry. That superconductors do not do the same thing when time runs backwards has implications on the application of these materials to electronics, which proceeds largely on the assumption that time is symmetric. This project will seek an understanding of why superconductors distort signals and will provide insight into how the distortion could be mitigated. Superconducting devices made by several companies have been acquired for use in this project. The bulk of this work will be done by a team of six to ten undergraduates pursuing degrees in physics and engineering. Along with learning in-demand skills such as microwave test and measurement and finite element analysis, students will learn to be effective researchers by developing experiment plans, presenting at conferences and contributing to publications in the peer reviewed literature.
