Andreev Reflections in Micrometer-Scale Normal-Insulator-Superconductor Tunnel Junctions

TL;DR

This paper investigates Andreev reflections in micrometer-scale NIS tunnel junctions, confirming that the multiple reflection theory accurately models subgap currents across various junction sizes and resistance products.

Contribution

The study provides experimental validation of the multiple Andreev reflection theory in NIS junctions of different sizes and resistance parameters.

Findings

Multiple Andreev reflection theory matches experimental data

Subgap current depends on junction area and resistance product

Theory applicable across various junction geometries

Abstract

Understanding the subgap behavior of Normal-Insulator-Superconductor (NIS) tunnel junctions is important in order to be able to accurately model the thermal properties of the junctions. Hekking and Nazarov developed a theory in which NIS subgap current in thin-film structures can be modeled by multiple Andreev reflections. In their theory, the current due to Andreev reflections depends on the junction area and the junction resistance area product. We have measured the current due to Andreev reflections in NIS tunnel junctions for various junction sizes and junction resistance area products and found that the multiple reflection theory is in agreement with our data.