Dendritic flux avalanches in Niobium single crystal near critical temperature

摘要

We report on the observation of dendritic flux avalanches in a large Niobiumsingle crystal. In contrast to avalanches observed in thin films, they appearonly in a very narrow temperature interval of about a tenth of a Kelvin nearthe critical temperature of Nb. At a fixed temperature, we find two sets ofdendritic structures, which differ by the magnetic field required for theirformation and by the maximum distance the dendrites penetrate into the sample.The effect is caused by dendritic flux penetration into thin superconductingsurface layers formed in the single crystal close to the critical temperature.