Korshunov instantons in a superconductor at elevated bias current

Abstract

Even at zero temperature dissipation reduces quantum fluctuations and tends to localize particles. A notable exception is the nonlinear dissipation due to quasiparticle tunneling in a Josephson junction. It is well known that quasiparticle dissipation does not suppress tunneling of the superconducting phase difference between next-nearest metastable phase states even though tunneling to the nearest phase state is suppressed. The reason is that the dissipative action admits an instanton solution, the so-called Korshunov instanton. Here, we analyze this model at elevated bias current I. We find that besides the known regime where the logarithm of the tunneling rate scales as I 2/3there is novel regime with a scaling I 2 . We argue that the increased tunneling rate that derives from the elevated bias current is favorable for an experimental verification of the Korshunov instantons.

Effects of a dissipative coupling to the momentum of a particle in a double well potential

“…Dissipative momentum and position couplings can be translated to dissipative charge or dissipative phase couplings in electrical quantum circuits, respectively [25]. In these systems a variety of effects, including dissipative quantum phase transitions have been observed [26][27][28]. In the frustrated case in presence of both phase and charge dissipation, the phase diagram of a superconducting chain shows a non monotonic behavior as function of the dissipative coupling [29].…”