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arXiv · 2501.11751

Quantum-geometric spin and charge Josephson diode effects

Niklas L. Schulz·Danilo Nikolić·Matthias Eschrig
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Abstract

We present a general mechanism for large charge and spin Josephson diode effects in strongly spin-polarized superconductor-ferromagnet hybrid structures with a noncoplanar spin texture, formulated in terms of quantum-geometric phases. We present necessary conditions for this effect to occur, and show numerical results for disordered materials, relevant for applications. We calculate Josephson diode efficiencies for both charge- and spin-diodes and show that a spin-diode efficiency of 100% can be reached. Finally, we present a SQUID device that can switch between nearly pure spin-up and spin-down equal-spin supercurrents across the ferromagnet by reversing the flux. These findings establish functionalities that are absent for coplanar spin textures.

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Niklas L. Schulz, Danilo Nikolić, Matthias Eschrig. 2025-10-31. Quantum-geometric spin and charge Josephson diode effects. https://doi.org/10.1103/nb38-v1jq

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