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

Abstract

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-WTe₂ barrier and NbSe₂ electrodes that clearly reflects the intrinsic crystal structure of T_d-WTe₂. The Josephson diode efficiency increases with the T_d-WTe₂ 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-WTe₂. Our results, together with the twist-angle-tuned magneto-chirality of a T_d-WTe₂ double-barrier junction, show that two-dimensional materials promise vertical Josephson diodes with high efficiency and tunability.

J.-K. Kim et al. study vertical Josephson junctions where the weak link is T_d-WTe₂ and the superconductor is NbSe₂. The use of an inversion-symmetry-breaking T_d-WTe₂ weak link allows the authors to demonstrate the intrinsic origin of the observed Josephson non-reciprocity in these devices.