Altermagnets are a recently identified class of magnets with zero net magnetisation but spin-split electronic bands. This theory study asks what happens when they meet superconductors in disordered, real-world materials. Starting from quantum kinetic transport equations, the authors derive a Ginzburg–Landau free energy that contains a new coupling between spin and spatial variations of the superconducting state.

Two effects follow: a supercurrent can induce a spin texture, and variations in the strength of superconductivity also create magnetisation, for example around vortices or next to superconductor/altermagnet interfaces. In Josephson junctions, the theory predicts 0–π transitions. QMAT researchers Tim Kokkeler and Stefan Ilić of the University of Jyväskylä's Condensed Matter Theory group wrote the paper with colleagues at the Centro de Física de Materiales and the Donostia International Physics Center in San Sebastián.

Figure: de las Heras et al., Phys. Rev. B (2026); image from arXiv:2512.04819, CC BY 4.0