Intrinsic supercurrent non-reciprocity coupled to the crystal structure of a van der Waals Josephson barrier.

Non-reciprocal electronic transport in a spatially homogeneous system arises from the simultaneous breaking of inversion and time-reversal symmetries. Superconducting and Josephson diodes, a key ingredient for future non-dissipative quantum devices, have recently been realized. Only a few examples of a vertical superconducting diode effect have been reported and its mechanism, especially whether intrinsic or extrinsic, remains elusive. Here we demonstrate a substantial supercurrent non-reciprocity in a van der Waals vertical Josephson junction formed with a T d -WTe 2 barrier and NbSe 2 electrodes that clearly reflects the intrinsic crystal structure of T d -WTe 2 . The Josephson diode efficiency increases with the T d -WTe 2 thickness up to critical thickness, and all junctions, irrespective of the barrier thickness, reveal magneto-chiral characteristics with respect to a mirror plane of T d -WTe 2 . Our results, together with the twist-angle-tuned magneto-chirality of a T d -WTe 2 double-barrier junction, show that two-dimensional materials promise vertical Josephson diodes with high efficiency and tunability.