Instantons in the out-of-equilibrium Coulomb blockade

TL;DR

This paper investigates non-perturbative instanton effects in out-of-equilibrium single-electron devices, revealing universal saddle-point behavior in the Ambegaokar-Eckern-Schoen action using Keldysh technique.

Contribution

It extends the understanding of instantons in Coulomb blockade to non-equilibrium states with a universal saddle-point value.

Findings

Identified instantons in non-equilibrium Ambegaokar-Eckern-Schoen action.

Discovered universal saddle-point value independent of non-equilibrium conditions.

Applied Keldysh technique to analyze out-of-equilibrium instantons.

Abstract

Physical properties of single-electron devices in the week Coulomb blockade regime are significantly dependent on non-perturbative effects. They arise as instanton solutions of equations of motion for the corresponding Ambegaokar-Eckern-Schoen action. In equilibrium those solutions are known as Korshunov instantons. In this paper we study non-equilibrium Ambegaokar-Eckern- Schoen action using Keldysh technique. We found instantons for the most general stationary out-of equilibrium state. We also found that action saddle-point value assumes a universal value irrespective of the stationary non-equilibrium state.