Thermal and quantum decay of supercurrent in highly transparent weak links

We analyze a trade-off between thermal activation (TA) and quantum tunneling in the problem of supercurrent decay in superconducting junctions with highly transparent barriers. In such systems – unlike in conventional tunnel junctions – the supercurrent decay is essentially influenced by low energy Andreev levels forming an intrinsic quantum dissipative environment for the Josephson particle. We evaluate the temperature dependent supercurrent decay rate Γ(T) and elucidate a variety of different regimes for such a decay. We demonstrate that no classical-to-quantum crossover exists in the limit of fully transparent barriers, in which case quantum tunneling always prevails over TA.