Bachelors Defense: Charlotte Bøttcher – University of Copenhagen

Bachelors Defense: Charlotte Bøttcher

Measuring the Superconductor-to-Insulator Transition in a Semiconductor Josephson Junction Array

In my thesis I present a superconductor/semiconductor hybrid system combined with a Josephson junction array (JJA), providing a new platform to study the superconductor-to-insulator transition (SIT). I present a system with gate-control of EC/EJ, and study a collection of parameter-tuned transitions, including temperature-, perpendicular magnetic-field- and gate-tuned transitions from a superconducting-to-insulating state and provide with a complete three parameter phase diagram for a semiconductor/superconductor JJA. A unique set of commensurability effects was observed when a magnetic field was applied perpendicular to the system, and I present a study of a current-driven transition from commensurated field minima to peaks, interpreted in context of a vortex insulating-to-dynamic vortex state. In an in-plane field study, I show a collapse of the critical scaling exponent as a function of higher in-plane field values.