Phase-dependent noise correlations in normal-superconducting structures

TL;DR

This paper investigates how nonequilibrium noise correlations in diffusive normal-superconducting structures depend on voltage, phase, and geometry, revealing the interplay of Andreev pair anticorrelation and local density of states effects.

Contribution

It introduces a parametrization of the quasiclassical Green's function to analyze noise correlations with supercurrent and describes the voltage and phase dependence in detail.

Findings

Low-voltage effective charge is influenced by competition between anticorrelation and density of states.

Noise correlations are independent of supercurrent direction.

Setup geometry significantly affects noise correlation behavior.

Abstract

We study nonequilibrium noise correlations in diffusive normal-superconducting structures in the presence of a supercurrent. We present a parametrization for the quasiclassical Green's function in the first order of the counting field $\chi$. This we employ to obtain the voltage and phase dependence of cross and autocorrelations and to describe the role played by the setup geometry. We find that the low-voltage behavior of the effective charge $q_{\rm eff}$ describing shot noise is a result of a competition between anticorrelation of Andreev pairs due to proximity effect and the depression of the local density of states. Furthermore, we show that the noise correlations are independent of the sign of the supercurrent.