General transport properties of superconducting quantum point contacts: a Green functions approach

TL;DR

This paper uses a Green functions approach to analyze the transport properties of superconducting quantum point contacts, including current response, noise, and resonant level transport, with results aligning well with experimental data.

Contribution

It introduces a microscopic Green functions method to study superconducting quantum point contacts under various conditions, extending understanding of their transport behavior.

Findings

Transport properties match experimental data

Current fluctuations analyzed under different biases

Resonant level transport discussed

Abstract

We discuss the general transport properties of superconducting quantum point contacts. We show how these properties can be obtained from a microscopic model using nonequilibrium Green function techniques. For the case of a one-channel contact we analyze the response under different biasing conditions: constant applied voltage, current bias and microwave-induced transport. Current fluctuations are also analyzed with particular emphasis on thermal and shot-noise. Finally, the case of superconducting transport through a resonant level is discussed. The calculated properties show a remarkable agreement with the available experimental data from atomic-size contacts measurements. We suggest the possibility of extending this comparison to several other predictions of the theory.