Anomalous Behavior near T_c and Synchronization of Andreev Reflection in Two-Dimensional Arrays of SNS Junctions

TL;DR

This study explores low-temperature transport in 2D arrays of SNS junctions, revealing anomalous spectral changes and high harmonic SGS due to synchronization effects, involving conventional and crossed Andreev reflections.

Contribution

It demonstrates that 2D SNS arrays exhibit collective phenomena like spectral anomalies and high harmonic SGS, extending understanding of Andreev reflection in complex junction networks.

Findings

Spectral changes occur at energies near the Thouless energy despite thermal broadening.

High harmonic subharmonic energy gap structures are observed even with short energy relaxation lengths.

Synchronization of multiple SNS junctions influences transport properties and SGS formation.

Abstract

We have investigated low-temperature transport properties of two-dimensional arrays of superconductor--normal-metal--superconductor (SNS) junctions. It has been found that in two-dimensional arrays of SNS junctions (i) a change in the energy spectrum within an interval of the order of the Thouless energy is observed even when the thermal broadening far exceeds the Thouless energy for a single SNS junction; (ii) the manifestation of the subharmonic energy gap structure (SGS) with high harmonic numbers is possible even if the energy relaxation length is smaller than that required for the realization of a multiple Andreev reflection in a single SNS junction. These results point to the synchronization of a great number of SNS junctions. A mechanism of the SGS origin in two-dimensional arrays of SNS junctions, involving the processes of conventional and crossed Andreev reflection, is proposed.