Tunable magnetic flux avalanches triggered by a focalized laser spot

Abstract
Magnetic flux avalanches caused by thermomagnetic instabilities are a common phenomenon occuring in type II superconducting films. The unpredictability of these catastrophic events threaten the application of superconducting thin film equipment, such as high-temperature superconducting magnets. In the present work, through the fast Fourier transform method, we numerically investigate artificially triggered flux avalanches in superconducting films by a focalized laser, unveiling new features beyond naturally occurring avalanches. The numerical modeling is validated by reproducing previous experimental results. We investigate the effects of laser irradiation on the nucleation and evolution of flux avalanches for different cases, namely varying the laser irradiation position, laser power, laser-spot size, ramping rate of applied magnetic field and working temperature. We find that the laser irradiation can control and guide the position of flux avalanche at applied magnetic fields with small ramping rate, while the similar guidance effect cannot be observed at high ramping field. We demonstrate that such phenomenon can be tuned by environmental temperature, and the mechanism can be revealed by current crowding and local temperature around the laser spot. Furthermore, by considering a pair of laser spots, we observe two tunable scenarios by the laser power, (i) single flux avalanche triggered at one of laser spots and (ii) double flux avalanches triggered at both laser spots.