Hope College Physics Department
Research Experiences for Undergraduates
Summer 2008
Project Summary


Project Title: Microwave Probing of the Nonlinear Electrodynamics of Tl2Ba2CaCu2O 8-y
Student Name: Bradley Dober
Student's Home Institution: University of Wisconsin, Madison
Research Advisor: Dr. Stephen Remillard
Source of Support: This material is based upon work supported by the National Science Foundation under NSF-REU Grant No. PHY-0452206.
An understanding of the nonlinear electrodynamics of TBCCO superconductors is crucial to their ultimate application in microwave electronics. Surface resistance and its power dependence of TBCCO thin film wafers was measured before and after hole auto-doping at various temperatures. After nitrogen anneals, ranging from 250°- 350°C, surface resistance increased with doping, and the films moved to a higher nonlinear regime. Harmonic interference and intermodulation distortion (IMD) was measured in TBCCO patterned strip-line resonators. IMD peaked near 84 K, indicating that the shrinking superfluid density is more sensitive to current excitation. The generated intermodulation power is proportional to (Hmax)3.67, where Hmax is the maximum surface magnetic field. The location of second order harmonics was found to be different than that of third order within the patterned resonator.

__________________________________________________________________________________________________________________________________________________________ Publications and Presentations:
"Synchronous measurement of even and odd order intermodulation distortion at the resonant frequency of a superconducting resonator", Evan K. Pease, Bradley J. Dober, and S.K. Remillard, Review of Scientific Instruments, vol. 81, 024701 (2010).
"Harmonic and Intermodulation Distortion in a Superconducting Microwave Resonator" , Bradley Dober and S.K. Remillard, APS March Meeting, Pittsburgh, March 2009.