Visualizing Non-reciprocal Supercurrent Flow of Josephson Diode Effect

The Josephson diode effect (JDE) is a non-reciprocal, non-linear effect that is akin to the semiconductor diode effect but without dissipation, which promises to unlock new classical and quantum applications based on superconducting electronics. The material platforms to realize JDE are diverse, however, the exact mechanisms are still elusive. For instance, while time reversal and inversion symmetry breakings are necessary conditions for JDE, they alone are not sufficient. In this work we used a scanning quantum sensing microscope based on nitrogen vacancy centers in diamond to directly reveal the forward and backward supercurrent in a Josephson diode. We will show that a super current induced phase that arises from the kinetic inductance of the superconductor can offer a way to control the JDE. This new mechanism of JDE is particularly relevant when the superfluid density is low, such as in van der Waals superconductors.