Phase Sensitive Shot Noise in an Andreev Interferometer

TL;DR

This paper studies phase-sensitive shot noise in a diffusive Andreev interferometer, revealing how magnetic flux modulates noise and indicating phase-dependent pair correlations, with results aligning with advanced theoretical models.

Contribution

It demonstrates phase-sensitive shot noise modulation in an Andreev interferometer and links it to pair correlations, advancing understanding of nonequilibrium fluctuations in hybrid superconducting devices.

Findings

Shot noise is modulated by magnetic flux in the interferometer.

Effective charge shows phase-dependent deviations from 2e.

Experimental results agree with extended Keldysh Green's function theory.

Abstract

We investigate nonequilibrium noise in a diffusive Andreev interferometer, in which currents emerging from two Normal metal/Superconductor (N-S) interfaces can interfere. We observe a modulation of the shot noise when the phase difference between the two N-S interfaces is varied by a magnetic flux. This is the signature of phase-sensitive fluctuations in the normal metal. The effective charge inferred from the shot noise measurement is close to q_eff=2e but shows phase-dependent deviations from 2e at finite energy, which we interprete as due to pair correlations. Experimental data are in good agreement with theoretical predictions based on an extended Keldysh Green's function approach.