Simulation of the initial response of a high Tc superconducting film submitted to a voltage source

We present a model describing the response in the microsecond timescale of a superconducting high T-c thin film connected to a voltage source. The model is based on the existence of a critical current density j*(T), above which a highly dissipative state is observed in superconducting thin films. We use its experimental temperature dependence to calculate the current as a function of time, flowing into a YBa2Cu3O7 bridge deposited on a sapphire substrate. Unlike the usual hot spot picture, our model accounts for the similarity of the descriptions found in various reports treating the switching of fault current limiters based on superconducting thin films. In particular, our calculation exhibits the main observed features: after the voltage is turned on, the current density peaks in a few microseconds to a well defined value, then it decreases rapidly and stabilizes to approximately half of this peak value.