Shot Noise of Mesoscopic NS Structures: The Role of Andreev Reflection

TL;DR

This paper investigates how Andreev Reflection influences shot noise in mesoscopic normal-superconductor structures, revealing insights into electron pairing, correlations, and quantum-classical noise crossovers through combined experimental and theoretical analysis.

Contribution

It provides a comprehensive experimental and theoretical study of shot noise affected by Andreev Reflection, including high-frequency measurements and full counting statistics analysis.

Findings

Andreev Reflection shifts the classical-to-quantum noise crossover.

Deviations in effective charge from 2e reveal electron pair correlations.

Good agreement between theory and experiment in phase-dependent noise measurements.

Abstract

Electronic properties of mesoscopic systems made of normal metal in contact with normal and superconducting reservoirs are determined by Andreev Reflection. We address both experimentally and theoretically how Andreev Reflection manifests itself in shot noise experiments and what physics can be deduced from such measurements. We report high frequency measurements in which Andreev Reflection affects the distribution statistics of the electronic excitations, resulting in a shift of the classical-to-quantum regime or equilibrium-to-shot noise crossovers. We also demonstrate that the effective charge carried by paired electrons contains more information: its deviation from 2e is related to correlations among pairs. This is exemplified by the measurement of phase dependent noise in an Andreev Interferometer. The use of full counting statistics allows us to understand how the correlations occur, and its application to the case of the Andreev Interferometer exhibits a very good agreement between theory and experiment.