Researchers at the University of Central Florida have produced the first spin-resolved photoemission evidence of altermagnetism in Co1/4TaSe2, a cobalt-intercalated transition-metal dichalcogenide (TMD). The result, published October 5, 2026 in Nature Communications 17(1) (DOI: 10.1038/s41467-026-76784-x), adds a thin, tunable layered material to the short list of confirmed altermagnets — compounds that can inject and detect spin-polarized currents without the stray magnetic fields produced by conventional ferromagnets.

What did the team actually measure?

UCF Professor of Physics Madhab Neupane's group ran angle-resolved photoemission spectroscopy (ARPES) followed by spin-resolved ARPES on bulk single crystals of Co1/4TaSe2. The first pass mapped a band splitting in the electronic structure; the second confirmed that the two split bands carried opposite spin polarizations, the experimental fingerprint that defines altermagnetism.

"Our approach was to use higher-resolution methods that were insensitive to the electron's spin to measure the splitting in the energy levels," Neupane said. "Then, we complemented this measurement with spin-resolved ARPES to conclusively tell if this looks like altermagnetism."

Collaborators grew the high-quality samples. Neupane's team then screened surfaces before mapping electronic states — sample cleanliness is critical because photoemission sees only the outermost atomic layers.

"The significance became clear once the experimental measurements consistently matched our theoretical predictions," Neupane said. "Seeing those independent pieces of evidence converge gave us confidence that we had identified a genuine layered altermagnet."

Why does a layered material matter for chips?

Prior altermagnet candidates — ruthenium dioxide and certain manganese tellurides — sit as bulk crystals. Co1/4TaSe2 belongs to the TMD family, the same class that produced monolayer MoS2 and WS2 prototypes explored in 2D transistor research. Magnetic cobalt atoms sit between weakly bonded layers, allowing researchers to exfoliate thin films suitable for back-end-of-line or heterogeneous integration schemes being scoped for sub-2 nm logic and embedded nonvolatile memory.

"Evidence for altermagnetism in a versatile materials platform opens a lot of new possibilities," said Milo Sprague, the study's lead graduate student researcher. "There's currently a lot of debate in altermagnetic theory about how the spin-polarized electronic states interact with other magnetic phenomena. Now we have a material that we can easily modify to explore these questions."

Where the magnetic signal sits

The ARPES maps showed that the spin-polarized state originates in the bulk of the crystal, not just at the cleaved surface. Bulk-derived states couple more easily with metal contacts and drive transport signatures — the metrics device engineers will ultimately want to see.

How does this fit spintronics?

Conventional CMOS moves charge. Spintronics tries to move spin, ideally at lower switching energy per bit. Ferromagnets inject spin-polarized currents but emit stray fields that scale poorly as pitch shrinks below 10 nm. Antiferromagnets are field-quiet but lack useful spin-split bands. Altermagnets claim both. Neupane framed the value proposition directly:

"These materials are distinguished from more conventional antiferromagnets by their ability to generate and detect spin currents without the negative effect of producing stray fields," he said. "This new property makes them very well positioned for use in many different applications — including spintronics, ultrafast memory devices, terahertz networks and energy-efficient electronics."

Theorist Igor I. Mazin of George Mason University is a co-author; Mazin's group shaped much of the modern altermagnetism framework now being tested experimentally.

What's still unknown

The paper leaves open the mechanism by which altermagnetic order forms in Co1/4TaSe2 and how it interacts with competing magnetic arrangements. Transport measurements — anomalous Hall response, spin-torque efficiency, magnetoresistance — are the next data points engineers will want before any device integration becomes plausible.

"As electronic devices continue to shrink, researchers need new materials that can operate faster while consuming less energy," Neupane said. "If this approach proves viable, then layered altermagnets will be at the forefront of electronics development."

Funding came from the U.S. Department of Energy Office of Science under Award DE-SC0024304.