Switching of YBCO thin films into the dissipative state at high current densities

We report on the switching properties at high current densities of YBCO thi n films shunted by an Ag layer. These experiments are performed either in l iquid nitrogen or liquid argon (87.3K). Different transition regimes associ ated to specific electric field thresholds are observed. The nature of the thermal exchange with the bath and the role of the silver shunt and substra te are discussed. While only two regimes in the current-voltage characteris tics are observed in liquid nitrogen, successively reversible and hystereti c, an intermediate behaviour appears at 87.3K associated with a total curre nt diversion by the silver layer.