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  • Featured in Physics
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Persistent Spin Currents in Superconducting Altermagnets

Kyle Monkman1, Joan Weng1, Niclas Heinsdorf1,2, Alberto Nocera1, Yafis Barlas3, and Marcel Franz1

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Phys. Rev. X 16, 011057 – Published 16 March, 2026

DOI: https://doi.org/10.1103/52wh-1z5y

Abstract

Superconductors are famously capable of supporting persistent electrical currents, that is, currents that flow without any measurable decay as long as the material is kept in the superconducting state. We introduce here a class of materials—superconducting altermagnets—that can both generate and carry persistent spin currents. This includes spin-polarized electrical supercurrent as well as pure spin supercurrent that facilitates spin transport in the absence of any charge transport. A key to this remarkable property is the realization that the leading superconducting instability of altermagnetic metals consists of two independent condensates formed of spin-up and spin-down electrons. In the nonrelativistic limit, the two condensates are decoupled and can, thus, naturally support persistent currents with any spin polarization, including pure spin supercurrents realized in the charge counterflow regime. We describe a novel “spin-current dynamo effect” that can be used to generate pure spin supercurrent in such systems by driving a charge current along certain crystallographic directions. Away from the nonrelativistic limit, when spin-orbit interactions and magnetic disorder are present, we find that the spin current generically develops spatial oscillations but, importantly, no dissipation or decay. This is in stark contrast to spin currents in normal diffusive metals which tend to decay on relatively short length scales. We illustrate the above properties by performing model calculations relevant to two distinct classes of altermagnets and various device geometries.

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Spin Supercurrents in Superconducting Altermagnets

Published 16 March, 2026

Materials from a new class of magnets could host permanent dissipationless spin currents when they enter a superconducting state.

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Popular Summary

Characterizing the transport properties of altermagnets is a significant challenge because these materials combine the vanishing net magnetization of antiferromagnets with the spin-split electronic structures of ferromagnets. We investigated the emergence of superconducting states within these materials and predicted that they host persistent spin currents that flow without any dissipation. Our analysis suggests that these spin-polarized supercurrents behave analogously to the charge supercurrents found in conventional superconductors but carry a net spin angular momentum instead. We found that this dissipationless flow remains stable against modest perturbations, providing a robust mechanism for transporting magnetic information. These results establish altermagnetic superconductors as a versatile platform for the field of spintronics and offer a new path for developing ultra-low-power components for future computing technologies.

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Phys. Rev. X 16, 011057– Published 16 March, 2026
  • Received 5 August 2025
  • Revised 17 October 2025
  • Accepted 26 January 2026
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