Hope College Physics Department
Research Experiences for Undergraduates
Summer 2013
Project Summary


Project Title: Nonlinearity generating hot spots in patterned superconducting films
Student Name: Dustin Kirkendall
Student's Home Institution: Grand Valley State University
Research Advisor: Dr. Stephen Remillard
Source of Support:

This project was supported by the National Science Foundation Grant No. DMR-1206149 and Grant No. PHY/DMR-1004811.

High temperature superconductor (HTS) microwave resonators respond nonlinearly to microwave current, and this nonlinearity can spike locally inside the device at hot spots. In a superconducting film with an engineered defect, such as an ion implanted channel, we expect a nonlinearity hot spot to be produced inside the material at the location of the defect. The nonlinearity in patterned superconducting films was examined using a three-tone method to measure intermodulation distortion (IMD) in the resonant band of the superconducting device. A moveable probe performed line scans of the locally generated IMD to give an indication as to where nonlinear behavior was most prominent. The third order IMD was found to be more local than second order IMD, so the third order IMD was used for mapping the nonlinearity hot spots. In an unaltered hairpin superconducting film, nonlinearity hot spots were observed in the corners or turns of the transmission line. However, the hairpin superconducting resonator engineered with an ion implanted channel exhibited an enhanced peak in third order IMD at the location of the channel with significantly diminished IMD in the rest of the resonator.

Publications and Presentations: