# Imaging doubled shot noise in a Josephson scanning tunneling microscope

## TL;DR

This study uses a Josephson scanning tunneling microscope to spatially resolve current noise, revealing the transition from single-electron to double-electron charge transfer below the superconducting gap, demonstrating homogeneous charge pairing.

## Contribution

It provides the first spatially resolved imaging of doubled shot noise in a Josephson STM, linking noise behavior to superconducting properties at atomic resolution.

## Key findings

- Doubling of shot noise occurs below the superconducting gap.
- Charge pairing is homogeneous across the surface, unaffected by small impurities.
- Transition from single to double charge transfer is clearly observed as bias varies.

## Abstract

We have imaged the current noise with atomic resolution in a Josephson scanning tunneling microscope with a Pb-Pb junction. By measuring the current noise as a function of applied bias, we reveal the change from single electron tunneling above the superconducting gap energy to double electron charge transfer below the gap energy when Andreev processes become dominant. Our spatially resolved noise maps show that this doubling occurs homogeneously on the surface, also on impurity locations, demonstrating that indeed the charge pairing is not influenced by disruptions in the superconductor smaller than the superconducting coherence length.