Imaging local supercurrent density in planar Josephson junction [Part 1]*

Josephson junctions exhibit macroscopic coherent quantum tunneling and are central

superconducting elements that are widely used for quantum sensing and quantum technology

applications. However, direct imaging of the coherent interference of supercurrent flow in the

junction is still missing. Here, using a scanning Nitrogen-vacancy center in diamond, we report high

resolution, direct visualization of Josephson vortices in a diffusive superconducting-normal-

superconducting (SNS) junction. The supercurrent flow evolves with external current bias and threaded

flux, as the phase difference of the superconducting electrodes is tuned. We establish local scanning

magnetometry as a feasible way to measure Josephson junctions made of quantum materials.