Superconducting diode effect in Al–InAs planar Josephson junctions

The superconducting diode effect has garnered recent attention in part due to its potential to reveal intrinsic properties of a material system. We study critical current nonreciprocity in Al–InAs planar Josephson junctions as a function of superconducting electrode width, gate voltage, and in-plane magnetic field magnitude and angle. From the electrode width scaling behavior, we determine the coherence length of the Andreev bound states in the junction and the in-plane magnetic flux at which the nonreciprocity is maximized. At small magnetic fields, we observe a gate-tunable diode polarity associated with the anomalous phase shift. The angular dependence of the nonreciprocity further reveals the presence of a third harmonic. The data are consistent with a model of finite momentum Cooper pairs induced by spin–orbit coupling and Zeeman interaction.