title: Observation of Transient Overcritical Currents in YBCO Thin Films using High-Speed Magneto-Optical Imaging and Dynamic Current Mapping.
abstract: The dynamics of transient current distributions in superconducting YBa2Cu3O7-δthin films were investigated during and immediately following an external field ramp, using high-speed (real-time) Magneto-Optical Imaging and calculation of dynamic current profiles. A number of qualitatively unique and previously unobserved features are seen in this novel analysis of the evolution of supercurrent during penetration. As magnetic field ramps up from zero, the dynamic current profile is characterized by strong peaks, the magnitude of which exceed the conventional critical current density (as determined from static current profiles). These peaks develop close to the sample edges, initially resembling screening currents but quickly growing in intensity as the external field increases. A discontinuity in field and current behaviour is newly observed, indicating a novel transition from increasing peak current toward relaxation behaviour. After this transition, the current peaks move toward the centre of the sample while reducing in intensity as magnetic vortices penetrate inward. This motion slows exponentially with time, with the current distribution in the long-time limit reducing to the expected Kim-model profile.
authors.affiliation: Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
authors.forename: Frederick S
authors.initials: FS
authors.lastname: Wells
authors.affiliation: Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.|National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoye Shosse, 115409, Moscow, Russian Federation.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Pan
authors.affiliation: Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.|Laboratory of Topological Quantum Phenomena in Superconducting Systems, Moscow Institute of Physics and Technology, State University, 9 Institutskiy per., Dolgoprudny, Moscow Region, 141700, Russia.|Laboratory of Superconducting Metamaterials, National University of Science and Technology MISIS, 4 Leninsky prosp., Moscow, 119049, Russia.
authors.forename: Igor A
authors.initials: IA
authors.lastname: Golovchanskiy
authors.affiliation: Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.|Center for Medical &Radiation Physics, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Fedoseev
authors.affiliation: Center for Medical &Radiation Physics, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
authors.forename: Anatoly
authors.initials: A
authors.lastname: Rozenfeld