Vortex avalanches and self organized criticality in superconducting   niobium
  In 1993 Tang proposed [1] that vortex avalanches should produce a self organized critical state in superconductors, but conclusive evidence for this has heretofore been lacking. In the present paper, we report extensive micro-Hall probe data from the vortex dynamics in superconducting niobium, where a broad distribution of avalanche sizes scaling as a power-law for more than two decades is found. The measurements are combined with magneto-optical imaging, and show that over a widely varying magnetic landscape the scaling behaviour does not change, hence establishing that the dynamics of superconducting vortices is a SOC phenomenon. 
E. Altshuler, T.H. Johansen, Y. Paltiel, Peng Jin, K.E. Bassler, O.   Ramos, G.F. Reiter, E. Zeldov, and C.W. Chu