Realization of the field-free Josephson Diode

: The superconducting analog to the semiconducting diode, the Josephson diode, has long been sought with multiple avenues to realization proposed by theorists 1-3 . Exhibiting magnetic field free, single directional superconductivity with Josephson coupling, it would serve as the building block for next generation superconducting circuit technology. Here we realized the Josephson diode by fabricating an inversion symmetry breaking van der Waals heterostructure of NbSe 2 /Nb 3 Br 8 /NbSe 2 . We demonstrate, for the first time without magnetic field, that the junction can be superconducting with positive current while resistive with negative current. The ∆ I c behavior (the difference between positive and negative critical currents) with magnetic field is symmetric and Josephson coupling is proven through the Fraunhofer pattern. Also, stable half-wave rectification of a square-wave excitation was achieved with a very low switching current density, high rectification ratio and high robustness. This nonreciprocal behavior strongly violates the known Josephson relations and opens the door to discover new mechanisms and physical phenomena through integration of quantum materials with Josephson junctions, and provides new avenues for phenomena when integrating quantum material barriers leading to novel or anomalous Josephson phenomena through the effect of the intrinsic properties of the barrier. Future work combining materials possessing properties such as topological states, ferroelectricity, magnetoelectricity, noncollinear magnetism, obstructed atomic insulator and emergent properties from twisted heterostructures, with superconducting electrodes may allow the realization of novel Josephson phenomena. Thus the opportunities for creating superconducting electronics utilizing quantum materials are vast and just beginning. inversion symmetry, the field-free Josephson diode effect dose not occur. These results, along with the observations in NbSe 2 /Nb 3 Br 8 /NbSe 2 devices (Device #1 and Device #3), indicate that the field-free Josephson diode effect originates from asymmetric Josephson tunnelling induced by the Nb 3 Br 8 barrier and the associated NbSe 2 /Nb 3 Br 8 interfaces in the junction.