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Direct observation of a superconducting vortex diode.

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Matsuki, Hisakazu 
Gorzawski, Laura 


The interplay between magnetism and superconductivity can lead to unconventional proximity and Josephson effects. A related phenomenon that has recently attracted considerable attention is the superconducting diode effect, in which a nonreciprocal critical current emerges. Although superconducting diodes based on superconductor/ferromagnet (S/F) bilayers were demonstrated more than a decade ago, the precise underlying mechanism remains unclear. While not formally linked to this effect, the Fulde-Ferrell-Larkin-Ovchinikov (FFLO) state is a plausible mechanism due to the twofold rotational symmetry breaking caused by the finite center-of-mass-momentum of the Cooper pairs. Here, we directly observe asymmetric vortex dynamics that uncover the mechanism behind the superconducting vortex diode effect in Nb/EuS (S/F) bilayers. Based on our nanoscale SQUID-on-tip (SOT) microscope and supported by in-situ transport measurements, we propose a theoretical model that captures our key results. The key conclusion of our model is that screening currents induced by the stray fields from the F layer are responsible for the measured nonreciprocal critical current. Thus, we determine the origin of the vortex diode effect, which builds a foundation for new device concepts.


Acknowledgements: We thank O. Agam, D. Orgad, E. Zeldov, and A. Kamra for fruitful discussions. This work was supported by the European Research Council (ERC) Foundation Grant No. 802952 (Y.A.), the EPSRC through the Core-to-Core International Network “Oxide Superspin” (Grant No. EP/P026311/1) (J.W.A.R.), the French National Agency for Research, Idex Bordeaux (Research Program GPR Light) and the EUR Light S&T (V.P. and A.B.). The international collaboration on this work was fostered by the EU-COST Action Nanocohybri CA16218 and Superqumap CA21144.

Funder: European Research Council (ERC) Foundation Grant No. 802952 EU-COST Action nanocohybri CA16218 EU-COST Action superqumap CA21144.


Article, /639/301/119/1003, /639/301/119/2793, /639/925/927/1064, /639/766/119/544, /639/766/119/995, article

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Nat Commun

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Springer Science and Business Media LLC
Engineering and Physical Sciences Research Council (EP/P026311/1)