Voltage-tunable field-free Josephson diode

We report a gate-tunable Josephson diode effect in hybrid nanowire junctions consisting of a spin-orbit-coupled semiconductor core coated with epitaxial ferromagnetic insulator and superconductor shells. The wires display a hysteretic superconducting window as a function of axial magnetic field. In the superconducting regime, the devices exhibit nonreciprocal supercurrent transport, with the diode efficiency showing a strong dependence on back-gate voltage. The effect persists in a remanent magnetization state following a controlled demagnetization procedure, establishing zero-field operation. These findings demonstrate a voltage-controlled Josephson diode in a single junction and suggest a route toward probing intrinsically broken inversion and time-reversal symmetries in hybrid materials.