Interfaces between magnets and superconductors are central to superconducting spintronics, but modelling them requires accurate boundary conditions. Tim Kokkeler of QMAT's Condensed Matter Theory group at the University of Jyväskylä, with Yukio Tanaka of Nagoya University and Sebastian Bergeret in San Sebastián, presents general boundary conditions for spin-active interfaces involving diffusive materials.

Derived with the action formalism, they hold in both normal and superconducting states and also give the full counting statistics of charge, heat and spin currents. The authors apply them to the anomalous proximity effect and to Josephson junctions involving triplet and spin-split superconductors, showing that anomalous Josephson currents come with a diode effect only when the spin-up and spin-down transparencies are both nonzero and distinct.

The preprint has not yet been peer reviewed.

Figure: Kokkeler et al., arXiv:2610.06486 (2026), CC BY 4.0