Charge Imbalance Transport in a Superconducting Wire with Spatial Variation of Pair Potential Amplitude

Abstract

We study charge imbalance transport in a superconducting wire with focus on the influence of spatial variation of pair potential amplitude Δ. Assuming that a superconducting wire is coupled to two normal-metal electrodes via tunnel junctions, we consider the case in which charge imbalance is created at one junction and the resulting excess tunneling current I ex is measured at the other junction. If Δ is locally suppressed in a short region between the two junctions, charge imbalance is relaxed by Andreev scattering induced by spatial variation of Δ, resulting in a reduction of I ex . To observe this influence, we numerically calculate I ex by employing a Boltzmann equation approach. It is shown that even a small suppression of Δ strongly reduces I ex . This indicates that induced Andreev scattering significantly contributes to charge imbalance conversion.