LAUSR

We report measurements of the flux flow instability velocity in 8 nm thin superconducting NbRe microstrips. In particular, a change in vortex motion after the film has been lightly oxidised is observed. We propose a possible mechanism according to which pinning is caused by domain walls where the superconducting properties are discontinuous and support our claim by a toy-model time-dependent Ginzburg-Landau simulation. Since our model is very general and applies to any type-II superconductor, we expect similar effects on other air-sensitive ploycrystalline thin film superconductors.