Nonlinear Response of Combined Superconductor/Ferroelectric Devices: First Experimental Step

Superconducting thin films are known to possess a nonlinear response at microwave frequencies. These nonlinear effects can be described quantitatively by a nonlinear inductance, and for high-Tc superconductors, are believed to be an intrinsic consequence of d-wave superconductivity. Similar nonlinear effects can be observed in ferroelectric materials, such as SrTiO₃. We experimentally explore the interaction between nonlinear effects of different character arising from these two different origins. We consider a number of different device configurations, and measure the generation of harmonic and intermodulation products as function of temperature, in order to assess how these two different types of nonlinear response would interact in devices fabricated from both types of nonlinear materials. We use these measurements to assess whether nonlinear effects in high-Tc superconductor devices may be mitigated by some form of active cancellation. Effects of the ferroelectric losses are also discussed.