Magnetic field effect on the escape rate in Nb/AlOx/Nb josephson junctions

We studied the escape rate of Nb/AlOx/Nb Josephson junctions in zero and finite magnetic fields. The escape rate was determined from the distribution of the critical currents and the experimental data were fit to the theoretical model to determine effective temperatures, which govern the thermal activation over the energy barrier. The effective temperatures were found to depend strongly on the magnetic-field modulated critical current. We discuss a possible cause for the magnetic field dependence of the escape rate in terms of non-uniform current distribution in the junctions.