High Kinetic Inductance Coplanar Waveguide Resonators from 2D Superconducting Electron Gases at KTaO₃ Interfaces for Quantum Applications

We fabricated and characterized coplanar waveguide resonators using two-dimensional superconducting electron gases (2DEGs) at KTaO3 (111) interfaces. This interfacial 2DEG exhibits properties such as orientation-dependent superconducting transitions and carrier-density based tunability of superconductivity at low temperatures. Using a reflection measurement, temperature-dependent resonances are revealed at multiples of a fundamental frequency which corresponds to a large sheet kinetic inductance, which can be tuned by chemical doping or by changing temperature. The values for the sheet kinetic inductance surpass those reported on granular Al films with comparable superconducting transition temperatures. The combination of high kinetic inductance and large dielectric constant of KTaO3 (~4500) results in resonators with low phase velocities, small mode volumes, and low impedance. These have potential applications in superconducting electronics for quantum information science.