Dendritic flux avalanches in Niobium single crystal near critical temperature

TL;DR

This study observes dendritic flux avalanches in a Niobium single crystal near its critical temperature, revealing unique temperature-dependent behaviors and structural differences in flux penetration.

Contribution

It reports the first observation of dendritic flux avalanches in a bulk Niobium single crystal near its critical temperature, highlighting their temperature sensitivity and structural variations.

Findings

Avalanches occur only within a narrow temperature range near Tc.

Two distinct dendritic structures differ by formation magnetic field and penetration depth.

Dendritic flux penetration occurs in thin surface layers near Tc.

Abstract

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