Electric Control of Polarity in Spin-Orbit Josephson Diode

The effect of spin-orbit coupling in a Josephson diode has not been elucidated due to its interplay with the complexity of Josephson devices. Here, we systematically control local electric fields in epitaxial Al-InAs Josephson junctions under in-plane magnetic fields and observe a polarity reversal of the Josephson diode. We interpret this polarity reversal as an effect of field-tunable spin-orbit coupling on nonreciprocal Josephson currents. A theoretical model, accounting for Rashba and Dresselhaus spin-orbit couplings in a planar Josephson junction containing many transverse subbands, aligns with the observed polarity reversal and its dependence on magnetic field. Our finding addresses spin-orbit control in a Josephson diode, enabling manipulation of Josephson harmonics.

💡 Research Summary

In this work the authors investigate how spin‑orbit coupling (SOC) can be used to control the polarity of a Josephson diode (JDE) in epitaxial Al‑InAs planar junctions. The device consists of two identical superconductor‑normal‑superconductor (S‑N‑S) weak links fabricated on a high‑mobility InAs quantum well, each covered by an independent top gate. By applying local gate voltages the Rashba SOC strength (α) can be tuned electrostatically, while the Dresselhaus component (β) is set by the crystal symmetry. An in‑plane magnetic field (By) is applied perpendicular to the bias current (which flows along the