Cascade dynamics of thermomagnetic avalanches in superconducting films with holes

The submicrosecond dynamics of thermomagnetic avalanches in superconducting films with nonconducting holes (antidots) is considered. When such an avalanche reaches a hole, it is quickly filled with magnetic flux, and often its rim becomes unstable and a second avalanche is nucleated. In this work the time- and space-resolved behavior of such cascading avalanche behavior is determined using numerical simulations. Results are presented for films with holes of different shape. It is found that holes with sharp corners are those that most frequently create secondary avalanches, and they tend to nucleate in corners. Magneto-optical imaging of Nb films patterned with the same set of holes strongly supports the numerical results.