Kinetic roughening of penetrating flux fronts in high-T-c thin film superconductors

Kinetic roughening of flux fronts penetrating in superconducting thin films are studied by means of a high resolution magneto-optic technique. The rou ghening exponent (alpha = 0.64) and growth exponent (beta = 0.65) obtained from a dynamic scaling analysis of the initial stage of flux penetration an d, at small length scales, are characteristic for a static disorder dominat ed nonlinear diffusion such as also observed in the directed percolated dep inning model. At large length scale, alpha = 0.46 indicates a transition to wards dynamic stochastic disorder, similar to the behavior of Kardar-Parisi -Zhang systems. There is a striking similarity with the behavior of combust ion fronts in burning paper.