Superconducting altermagnets could carry spin without energy loss

Sam Jarman

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Researchers have proposed that a newly identified class of magnetic materials could extend the zero-resistance currents of superconductors to electron spins. Publishing their calculations in Physical Review X, Kyle Monkman and colleagues at the University of British Columbia propose how "altermagnets" could enable persistent spin currents to flow without dissipation. If confirmed experimentally, the effect could provide a powerful new platform for spintronics, where information is encoded in spin rather than electric charge.

The challenge of moving spins

The ability to transport spins over long distances is a central challenge in spintronics. In conventional metals and semiconductors, spin currents decay rapidly due to effects that randomize electron spins. One promising workaround has been superconducting spintronics, where dissipationless charge transport is combined with magnetic materials. However, these hybrid systems often suffer from intrinsic drawbacks, including stray magnetic fields that can interfere with nearby components, suppressing superconductivity.

First confirmed in 2024, altermagnets offer a potential way around these problems. Like antiferromagnets (where a magnetic dipole's spin is always opposite to those of its neighbors), they have zero net magnetization, avoiding unwanted magnetic fields.

But like ferromagnets, their crystal symmetry also endows them with "spin-split" electron bands—meaning spin-up and spin-down electrons have different energies, even while possessing the same momentum. This unusual combination has prompted growing interest in their potential to host unconventional superconducting states.

Two condensates, one exotic superconductor

In their study, Monkman's team propose that when altermagnets become superconducting, they naturally form an exotic state composed of two independent condensates: one of spin-up electron pairs and one of spin-down pairs. Unlike conventional superconductors, where electrons pair with opposite spins, altermagnets favor pairs with the same spin.

As a result, the superconducting state behaves like two separate fluids: one spin-up and one spin-down. When spin–orbit effects are weak, these fluids can flow independently.

This separation would lead to a striking possibility: if the two condensates flow in opposite directions, their charge currents would cancel, but their spin currents would add to each other. The result is a pure spin supercurrent—one that transports spin without any accompanying charge flow.

The team also identified a "spin-current dynamo effect," where an applied charge current can generate a transverse spin supercurrent in certain crystal orientations.

Robust currents and future prospects

Crucially, Monkman and colleagues show that these spin currents remain robust even when spin–orbit coupling and magnetic disorder are present. This behavior contrasts sharply with conventional materials, where spin currents typically vanish over short distances.

Although superconductivity has yet to be observed in known altermagnets, many candidate materials are good metals, suggesting that superconducting phases could emerge at low temperatures.

If realized experimentally, the researchers are hopeful that superconducting altermagnets could combine the advantages of magnetism and superconductivity without their usual trade-offs, offering new routes to low-power, spin-based technologies.

Written for you by our author Sam Jarman, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Kyle Monkman et al, Persistent Spin Currents in Superconducting Altermagnets, Physical Review X (2026). DOI: 10.1103/52wh-1z5y

Journal information: Physical Review X

Key concepts

MagnetismSuperconductivityQuantum many-body systems

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