Nucleation and propagation of thermomagnetic avalanches in thin-film superconductors (Review Article)
J.I. Vestgården1,2, T.H. Johansen1,3, and Y.M. Galperin1,4
1Department of Physics, University of Oslo, P.O. box 1048 Blindern, Oslo 0316, Norway
2Norwegian Defense Research Establishment (FFI), Kjeller, Norway
3Institute for Superconducting and Electronic Materials, University of Wollongong Northfields Ave., Wollongong, NSW 2522, Australia
4Ioffe Physical Technical Institute, 26 Polytekhnicheskaya, St Petersburg 194021, Russian Federation
Received December 14, 2017
Stability of the vortex matter — magnetic flux lines penetrating into the material — in type-II superconductor films is crucially important for their application. If some vortices get detached from pinning centres, the energy dissipated by their motion will facilitate further depinning, and may trigger an electromagnetic breakdown. In this paper, we review recent theoretical and experimental results on development of the above mentioned thermomagnetic instability. Starting from linear stability analysis for the initial critical-state flux distribution we then discuss a numerical procedure allowing to analyze developed flux avalanches. As an example of this approach we consider ultra-fast dendritic flux avalanches in thin superconducting disks. At the initial stage the flux front corresponding to the dendrite’s trunk moves with velocity up to 100 km/s. At later stage the almost constant velocity leads to a specific propagation regime similar to ray optics. We discuss this regime observed in superconducting films coated by normal strips. Finally, we discuss dramatic enhancement of the anisotropy of the flux patterns due to specific dynamics. In this way we demonstrate that the combination of the linear stability analysis with the numerical approach provides an efficient framework for understanding the ultra-fast coupled nonlocal dynamics of electromagnetic fields and dissipation in superconductor films.
PACS: 74.25.Qt Vortex lattices, flux pinning, flux crep;
Key words: vortex matter, thin-film superconductors, thermomagnetic instability.
Published online: April 25, 2018