The Theory of KTaO₃ DC-SQUIDs

The interfaces of LAO/KTO have been found to demonstrate superconductivity. In this talk we discuss theoretical modeling of DC-SQUIDs that we fabricated at the LAO/KTO interface via conductive atomic force microscope lithography. We find a periodic dependence of the device's critical current on magnetic field due to phase quantization around the device. This periodicity is shorter than anticipated based on the geometry of the device, and the oscillations demonstrate a phase offset from zero magnetic field. We model the supercurrents in the device and incorporate Dayem bridges of the device as short superconducting nanowires. Doing so, we understand the mechanism of the shortened oscillation period and are able to replicate the magnitude and phase oscillations of the critical current. We are also able to derive device parameters such as critical current, kinetic inductance, and effective length of the bridges. Our model identifies a large kinetic inductance of the superconducting 2DEG in KTO. Our demonstration and analysis of the SQUID effect in KTO also suggest it could provide a platform for future quantum devices.