Zero-field polarity-reversible Josephson supercurrent diodes enabled by a proximity-magnetized Pt barrier

Simultaneous breaking of inversion and time-reversal symmetries in a conductor yields a non-reciprocal electronic transport^1-3, known as the diode or rectification effect, that is, low (ideally zero) conductance in one direction and high (ideally infinite) conductance in the other. So far, most of the diode effects observed in non-centrosymmetric polar/superconducting conductors^4-7 and Josephson junctions^8-10 require external magnetic fields to break the time-reversal symmetry. Here we report zero-field polarity-switchable Josephson supercurrent diodes, in which a proximity-magnetized Pt layer by ferrimagnetic insulating Y₃Fe₅O₁₂ serves as the Rashba(-type) Josephson barrier. The zero-field diode efficiency of our proximity-engineered device reaches up to ±35% at 2 K, with a clear square-root dependence on temperature. Measuring in-plane field-strength/angle dependences and comparing with Cu-inserted control junctions, we demonstrate that exchange spin-splitting^11-13 and Rashba(-type) spin-orbit coupling^13-15 at the Pt/Y₃Fe₅O₁₂ interface are key for the zero-field giant rectification efficiency. Our achievement advances the development of field-free absolute Josephson diodes.