Synchronized Andreev Transmission in Chains of SNS Junctions

TL;DR

This paper develops a nonequilibrium theory for charge transfer in SNSNS junctions, revealing synchronized Andreev transmission phenomena that manifest as resonant spikes in differential conductivity.

Contribution

It introduces a novel nonequilibrium model showing how a central S-island acts as an Andreev retransmitter, leading to synchronized charge transfer in SNSNS chains.

Findings

Resonant spikes observed in differential conductivity.

Central S-island acts as an Andreev retransmitter.

Synchronization occurs at specific voltages.

Abstract

We construct a nonequilibrium theory for the charge transfer through a diffusive array of alternating normal (N) and superconducting (S) islands comprising an SNSNS junction, with the size of the central S-island being smaller than the energy relaxation length. We demonstrate that in the nonequilibrium regime the central island acts as Andreev retransmitter with the Andreev conversions at both NS interfaces of the central island correlated via over-the-gap transmission and Andreev reflection. This results in a synchronized transmission at certain resonant voltages which can be experimentally observed as a sequence of spikes in the differential conductivity.