Effect of magnetic field on macroscopic quantum tunneling escape time in small Josephson junctions

We study the phenomenon of macroscopic quantum tunneling (MQT) in a finite-size Josephson junction (JJ) with an externally applied magnetic field. As is well known, the problem of MQT in a pointlike JJ is reduced to the study of the under-barrier motion of a quantum particle in the washboard potential. In the case of a finite-size JJ placed in magnetic field, this problem is considerably more complex since, besides the phase, the potential itself depends on space variables. We find the general expressions both for the crossover temperature T₀ between thermally activated and MQT regimes and the escape time τ_esc . It turns out that in the proximity of particular values of magnetic field, the crossover temperature can vary nonmonotonically.