Josephson diode

A Josephson diode is an electronic device that superconducts electrical current in one direction and is resistive in the other direction. The device is a Josephson junction exhibiting a superconducting diode effect (SDE). It is an example of a quantum material Josephson junction (QMJJ), where the weak link in the junction is a quantum material.

Josephson diodes can be subdivided into two categories, those requiring an external (magnetic) field and those not requiring an external magnetic field; the so-called “field-free” Josephson diodes. In 2021, the field-free Josephson diode was realized.[1]

History
Example schematic of the first field free Josephson diode using NbSe2 and Nb3Br8.[1]

The Josephson diode is named after British physicist Brian David Josephson, who predicted the Josephson effect; and the resistive diode, since it has a similar function. In 2007 a "Josephson diode" was proposed with a design that was similar to conventional p-n junctions in semiconductor, but utilizing hole and electron doped superconductors.[2] This is different from the "Josephson fluxonic diode" that was introduced before the 2000s.[3][4][5][6] It is also different from how the term is currently used, where a Josephson diode is a Josephson junction exhibiting a superconducting diode effect.

In 2020, a superconducting diode effect was shown in an artificial [Nb/V/Ta]n superlattice.[7] A field-free superconducting diode effect was realized in 2021, in a van der Waals heterostructure of NbSe2/Nb3Br8/NbSe2 - a Josephson diode. This heterostructure is a quantum material Josephson junction, where the weak link (Nb3Br8) is a quantum material, that is predicted to be an obstructed atomic insulator / Mott insulator.[1][8][9][10]

The conductor used in the 2020 demonstration was non-centrosymmetric which breaks spatial symmetry, meaning it distinguishes between electrons with positive and negative momentum. In addition, the 2021 system also broke temporal symmetry – allowing spin-up electrons with positive momentum to behave differently from spin-down electrons with negative momentum.[11]

Superconducting diode effect

The superconducting diode effect is an example of nonreciprocal superconductivity, where a material is superconducting in one direction and resistive in the other. This leads to half-wave rectification when a square wave AC-current is applied. In 2020, this effect was demonstrated in an artificial [Nb/V/Ta]n superlattice.[7] The phenomenon in the Josephson diode is believed to originate from asymmetric Josephson tunneling.[1]

Theories

Currently, the precise mechanism behind the Josephson diode effect is not fully understood. However, some theories have emerged that are now under theoretical investigation. There are two types of Josephson diodes, relating to which symmetries are being broken. The inversion breaking Josephson diode and the inversion breaking plus time-reversal breaking Josephson diode. The minimal symmetry breaking requirement for forming the Josephson diode is inversion symmetry breaking.[12] The symmetry breaking is required to obtain nonreciprocal transport. Another proposed mechanism for short Josephson junctions, originates from finite momentum Cooper pairs.[13] It may also be possible that the superconducting diode effect in the JD originates from self-field effects, but this still has to be rigorously studied.[14][15]

References
  1. Wu, Heng; Wang, Yaojia; Xu, Yuanfeng; Sivakumar, Pranava K.; Pasco, Chris; Filippozzi, Ulderico; Parkin, Stuart S. P.; Zeng, Yu-Jia; McQueen, Tyrel; Ali, Mazhar N. (April 2022). "The field-free Josephson diode in a van der Waals heterostructure". Nature. 604 (7907): 653–656. arXiv:2103.15809. Bibcode:2022Natur.604..653W. doi:10.1038/s41586-022-04504-8. ISSN 1476-4687. PMID 35478238.
  2. Hu, Jiangping; Wu, Congjun; Dai, Xi (2007-08-09). "Proposed Design of a Josephson Diode". Physical Review Letters. 99 (6): 067004. Bibcode:2007PhRvL..99f7004H. doi:10.1103/PhysRevLett.99.067004. PMID 17930858.
  3. Raissi, F.; Nordman, J. E. (1994-10-03). "Josephson fluxonic diode". Applied Physics Letters. 65 (14): 1838–1840. Bibcode:1994ApPhL..65.1838R. doi:10.1063/1.112859. ISSN 0003-6951.
  4. Raissi, F.; Nordman, J.E. (June 1995). "Comparison of simulation and experiment for a Josephson fluxonic diode". IEEE Transactions on Applied Superconductivity. 5 (2): 2943–2946. Bibcode:1995ITAS....5.2943R. doi:10.1109/77.403209. ISSN 1558-2515. S2CID 34110010.
  5. Kadin, A. M. (1990-12-01). "Duality and fluxonics in superconducting devices". Journal of Applied Physics. 68 (11): 5741–5749. Bibcode:1990JAP....68.5741K. doi:10.1063/1.346969. ISSN 0021-8979.
  6. Nordman, James E.; Beyer, James B. (1995-06-13). "Superconductive Electronic Devices Using Flux Quanta". {{cite journal}}: Cite journal requires |journal= (help)
  7. Ando, Fuyuki; Miyasaka, Yuta; Li, Tian; Ishizuka, Jun; Arakawa, Tomonori; Shiota, Yoichi; Moriyama, Takahiro; Yanase, Youichi; Ono, Teruo (August 2020). "Observation of superconducting diode effect". Nature. 584 (7821): 373–376. doi:10.1038/s41586-020-2590-4. ISSN 1476-4687. PMID 32814888. S2CID 221182970.
  8. Xu, Yuanfeng; Elcoro, Luis; Song, Zhi-Da; Vergniory, M. G.; Felser, Claudia; Parkin, Stuart S. P.; Regnault, Nicolas; Mañes, Juan L.; Bernevig, B. Andrei (2021-06-17). "Filling-Enforced Obstructed Atomic Insulators". arXiv:2106.10276. {{cite journal}}: Cite journal requires |journal= (help)
  9. Xu, Yuanfeng; Elcoro, Luis; Li, Guowei; Song, Zhi-Da; Regnault, Nicolas; Yang, Qun; Sun, Yan; Parkin, Stuart; Felser, Claudia; Bernevig, B. Andrei (2021-11-03). "Three-Dimensional Real Space Invariants, Obstructed Atomic Insulators and A New Principle for Active Catalytic Sites". arXiv:2111.02433. {{cite journal}}: Cite journal requires |journal= (help)
  10. Zhang, Yi; Gu, Yuhao; Weng, Hongming; Jiang, Kun; Hu, Jiangping (2023). "Mottness in two-dimensional van der Waals Nb3X8 monolayers (X=Cl,Br,andI)". Physical Review B. 107 (3): 035126. arXiv:2207.01471. doi:10.1103/PhysRevB.107.035126. S2CID 255998779.
  11. "Scientists unveil Josephson diode". Physics World. 2022-05-04. Retrieved 2022-11-15.
  12. Zhang, Yi; Gu, Yuhao; Hu, Jiangping; Jiang, Kun (2022-07-10). "General Theory of Josephson Diodes". Physical Review X. 12 (4): 041013. arXiv:2112.08901. doi:10.1103/PhysRevX.12.041013. S2CID 245218901.
  13. Davydova, Margarita; Prembabu, Saranesh; Fu, Liang (2022-06-10). "Universal Josephson diode effect". Science Advances. 8 (23): eabo0309. doi:10.1126/sciadv.abo0309. ISSN 2375-2548. PMC 9176746. PMID 35675396.
  14. Goldman, A. M.; Kreisman, P. J. (1967-12-10). "Meissner Effect and Vortex Penetration in Josephson Junctions". Physical Review. 164 (2): 544–547. Bibcode:1967PhRv..164..544G. doi:10.1103/PhysRev.164.544.
  15. Yamashita, Tsutomu; Onodera, Yutaka (1967-08-01). "Magnetic‐Field Dependence of Josephson Current Influenced by Self‐Field". Journal of Applied Physics. 38 (9): 3523–3525. Bibcode:1967JAP....38.3523Y. doi:10.1063/1.1710164. ISSN 0021-8979.
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