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

TL;DR

This paper reports the discovery of intrinsic supercurrent non-reciprocity in a van der Waals Josephson junction, driven by the crystal structure of Td-WTe2, advancing the understanding of superconducting diode effects.

Contribution

It demonstrates that the supercurrent non-reciprocity is intrinsic to the crystal structure of Td-WTe2 in a vertical Josephson junction, with tunable efficiency and magneto-chiral properties.

Findings

Supercurrent non-reciprocity increases with Td-WTe2 thickness.

All junctions show magneto-chiral characteristics.

Intrinsic crystal structure influences supercurrent directionality.

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