7 May 2024 Tue 4 pm

We study the effect of the spin-orbit interaction, located at an electric point contact, on the Josephson tunneling of superconducting Cooper pairs. We demonstrate that such tunneling forces the electronic spin to fluctuate quantum mechanically, transforming a BCS condensate into a quantum superposition of singlet and triplet pairs. The relative admixture of those pairs can be controlled electrostatically and mechanically. The fraction of singlet pars is responsible for Josephson charge flow but not for Josephson spin current, flowing through the point contact, while the fraction of spin-polarized pairs contributes to an injected Josephson spin current, making no contribution to the superconducting charge flow. The above findings allow for new functionality of spin-active Josephson junctions.

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