Non-equilibrium transport near the disorder-driven SIT

We have measured the IV characteristics of square shaped TiN films on the superconducting and the insulating side of the superconductor-insulator transition. The superconducting IV characteristics display strong non-linearities including several jumps. The measured data was consistently reproduced in terms of electron heating models (''hotspot theory''), where the thermal conductivity in the superconducting parts of the film and the heat transfer coefficient per unit area to the substrate were used as free fitting parameters. On the basis of the hotspot theory, the obtained value for surface heat transfer coefficient seems to decrease drastically on approach of the disorder-driven SIT. At the same time, the thermal conductivity in the superconducting parts of the film appears to increase significantly on approach of the SIT. Independent thermal conductivity measurements are required to verify this interpretation. On the insulating side of the field-induced SIT the IV characteristics reveal a similar but dual non-linear behaviour. An analysis of the insulating IV characteristics in terms of selfheating in insulating microbridges is a future task.