# Shot noise as a probe for Andreev reflection in graphene-based heterojunctions

## TL;DR

This paper shows that shot noise measurements can effectively distinguish between retro and specular Andreev reflection in graphene-based heterojunctions, offering a new tool for probing microscopic transport mechanisms in quantum devices.

## Contribution

It introduces a method using shot noise spectroscopy to differentiate Andreev reflection types in graphene heterojunctions, supported by full wavefunction matching calculations.

## Key findings

- Distinct Fano factor signatures for retro and specular Andreev reflection
- Shot noise profiles are modified by multiple interfaces and phase variations
- Shot noise spectroscopy can complement conductance measurements in quantum device analysis

## Abstract

Shot noise emerges due to the discrete nature of charge transport and provides direct access to the underlying microscopic transport mechanisms governing current flow in mesoscopic conductors. In this work, we demonstrate that quantum shot noise offers a direct and robust fingerprint of Andreev reflection, distinguishing between retro and specular processes in graphene-superconductor, graphene-superconductor-graphene, and superconductor-graphene-superconductor junctions. At the graphene-superconductor interface, exact reflection amplitudes obtained from full wavefunction matching within the Bogoliubov-de Gennes formalism capture retro and specular regimes. The associated Fano factor exhibits distinct Fermi-level-dependent signatures, with retro Andreev reflection suppressing and specular Andreev reflection enhancing the shot noise. Extensions to graphene-superconductor-graphene and superconductor-graphene-superconductor configurations reveal how the transmission spectrum and, consequently, the noise profile are modified in the presence of multiple interfaces, coherent quasiparticle interference, and superconducting phase variations. Our findings establish shot noise spectroscopy as a potent and experimentally viable probe for differentiating Andreev reflection types in graphene-based quantum devices, providing complementary insights beyond conventional conductance measurements.