Active Superconducting Microwave Lumped Circuit Elements using High-T_c/Dielectric Multilayer Films

Abstract

We have studied the feasibility of a d. c. voltage bias controlled superconducting microwave lumped-circuit capacitor as an active device. A series-LC circuit was designed and fabricated using YBa₂Cu₃O₇/SrTiO₃ films. When a d. c. bias of 35 V was applied across the STO film at ~20 K, the total series capacitance of the circuit, measured at 1 MHz by an LCR meter, decreased by ~3% and the microwave resonant frequency of ~14 GHz increased by ~1.4%, in consistence with the predictions of a simple series-LC resonator model.