Electrodynamically and thermally driven flux flow in type I superconductors

A high resolution magneto-optic method employing EuS:EuF 2 films has been used to observe directly the dynamic intermediate state induced by the passage of an electric current or a heat current through thin slabs of the superconductors Pb, In and Sn. The observed flux flow velocities have been compared with and show reasonably good agreement with recent theoretical work by Andreev and Dzhikaev, if allowance is made for the effects of pinning. A detailed examination has been made of the region close to the critical current in the electric current induced motion. In the case of the thermally induced motion the existence of two competing mechanisms driving flux, as was recently suggested by Laeng and Rinderer, has been confirmed. Comparison has been made with theoretical models, again with some agreement and some disagreement.