Nonvolatile φ_₀-Memory and Symmetry Breaking in Helimagnetic Josephson Diodes

Chiral magnetic order in superconducting junctions enables intrinsic phase bias and broken time-reversal symmetry. We fabricate Josephson junctions from the helimagnet Cr_1/3NbS₂ and investigate how chiral spin textures control superconducting phase dynamics. Magnetic field training imprints persistent phase offsets (φ_₀) in the junction that survive after the field is removed. The junction's transport properties seem to violate microreversibility, exhibiting direction-dependent critical currents and odd-in-field asymmetries. The diode polarity itself can be reversed by changing how magnetic fields are applied. Our results demonstrate that symmetry-protected φ₀ states in helimagnetic junctions may enable reconfigurable, nonvolatile control of supercurrent directionality.