Developing superconducting resonators using the transition metal perovskite oxide Strontium Titanate

Coplanar superconducting resonators are crucial building blocks for various quantum computing architectures, quantum sensors and quantum memories. Strontium Titanate (STO) can be an exciting material platform for such emerging technologies, due to its high dielectric constant and semiconductor-like electrostatic tunability of superconductivity. In this study we have successfully fabricated planar hanger resonators (ranging from 2.8 to 3.3 mm in length) on 50 nm Nb thin films, grown by sputtering on (001) STO substrates. Through microwave transmission measurements, we observe fundamental resonance frequencies with additional harmonics in the 100 - 750 MHz range; this corresponds to a large dielectric constant of 40,000, which is consistent with incipient ferroelectric behavior of STO. These findings open up an exciting avenue for exploring extremely compact resonator geometries.