1 Quantum Physics and Information Techology, Department of Physics, Technical University of Denmark2 Department of Physics, Technical University of Denmark3 Nanointegration Group, NanoSystemsEngineering Section, Department of Micro- and Nanotechnology, Technical University of Denmark4 NanoSystemsEngineering Section, Department of Micro- and Nanotechnology, Technical University of Denmark5 Department of Micro- and Nanotechnology, Technical University of Denmark6 Center for Nanostructured Graphene, Center, Technical University of Denmark
It was predicted by Kibble and Zurek, that fast phase transitions in systems with degenerate ground states would produce topological defects. Although their work was initially focused on cosmological phase transitions, it was soon realized, that solid-state analogues existed. This opened the possibility of creating solid-state experiments and get results applicable to cosmological phase transitions. While dierent groups with several dierent approaches have tried to experimentally verify the critical scaling behavior of topological defect production in solid-state systems, the results have been far from convincing. In this project, the focus has been on designing, producing and using experimental setups focused on defect production in solid state systems. The system of choice is the annular Josephson junction, but the single superconducting ring has been used as an analogue as well. The results from the annular Josephson junction confirms critical scaling behavior of the probability of producing single fluxons with quench time, Q. The critical exponent found is AJT J = 0:5 5%. No scaling results have yet been obtained from the single superconducting ring experiments, but initial tests are promising. In addition to testing Kibble-Zurek theory, a major part of the project has been dedicated to measuring and modeling Josephson junctions of various geometries in out-of-plane fields. It was shown, that by careful design, the sensitivity of junctions to magnetic field direction could be modified. A theoretical model was found to explain this behavior, which was verified by experiments.