Realization of the field-free Josephson Diode

Heng Wu; Yaojia Wang; Yuanfeng Xu; Pranava K. Sivakumar; Chris Pasco; Ulderico Filippozzi; Stuart S. P. Parkin; Yu-Jia Zeng; Tyrel McQueen; Mazhar N. Ali

doi:10.1038/s41586-022-04504-8

paper

Realization of the field-free Josephson Diode

arXiv:2103.15809 · doi:10.1038/s41586-022-04504-8

Abstract

The superconducting analog to the semiconducting diode, the Josephson diode, has long been sought, with multiple avenues to realization proposed by theorists. Exhibiting magnetic-field free, single directional superconductivity with Josephson coupling of the supercurrent across a tunnel barrier, it would serve as the building-block for next-generation superconducting circuit technology. Here we realized the field-free Josephson diode using an inversion symmetry breaking heterostructure of $NbS e_{2} /N b_{3} B r_{8} /NbS e_{2}$ . We demonstrate, for the first time without magnetic field, the junction can be superconducting in one direction while normal in the opposite direction. Based on that, half-wave rectification of a square-wave excitation was achieved with low switching current density ( $2.2 \times 1 0^{2} A/c m^{2}$ ), high rectification ratio ( $1 0^{4}$ ) and high robustness (at least $1 0^{4}$ cycles). We also demonstrate symmetric $Δ I_{c}$ (the difference between positive and negative critical currents) behavior with field and the expected Fraunhofer current phase relation of a Josephson junction. This realization raises fundamental questions about the Josephson effect through an insulator when breaking symmetry, and opens the door to ultralow power, high speed, superconducting circuits for logic and signal modulation.

30 pages, 14 figures

Realization of the field-free Josephson Diode

Abstract

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