Effects of Low Energy Excitations in SNS Junction on the Dynamics of Josephson Phase

TL;DR

This paper investigates how low energy excitations in SNS junctions influence Josephson phase dynamics, deriving an effective action and analyzing the impact of retardation effects, leading to renormalized parameters affecting system behavior.

Contribution

It introduces a microscopic derivation of the effective phase action considering low energy excitations and analyzes their impact on Josephson dynamics through renormalized parameters.

Findings

Retardation effects significantly influence phase dynamics.

Mass is enhanced, dissipation is suppressed due to low energy excitations.

Different dynamical regimes emerge based on renormalized parameters.

Abstract

The effect of low energy excitation on the dynamics of Josephson phase in SNS junction is investigated. From the microscopic Hamiltonian, the effective action for the phase variable is derived. The retardation effects due to low energy excitation in normal(N) region are seen to play important roles in the dynamics of the phase. By the self consistent harmonic approximation, renormalization of mass and dissipation constant are calculated, revealing the enhancement of the former and the suppression of the latter in general. Various situation appears depending on these renormalized values.