UBC Proposes Persistent Spin Supercurrents in Altermagnets
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- Kyle Monkman and colleagues at the University of British Columbia published calculations in Physical Review X theorizing that superconducting altermagnets could carry persistent spin currents without dissipation.
- Altermagnets, first confirmed in 2024, combine zero net magnetization (like antiferromagnets) with spin-split electron bands (like ferromagnets), avoiding stray magnetic fields while retaining spin polarization.
- The team proposes superconducting altermagnets would form two independent condensates — spin-up and spin-down electron pairs — unlike conventional superconductors where electrons pair with opposite spins.
- If the two condensates flow in opposite directions, their charge currents cancel while spin currents add, producing a pure spin supercurrent that transports spin with no accompanying charge flow.
- The researchers also identified a "spin-current dynamo effect," where an applied charge current generates a transverse spin supercurrent in certain crystal orientations.
- These spin currents remain robust even with spin-orbit coupling and magnetic disorder present — unlike in conventional materials, where spin currents typically decay rapidly over short distances.
- Superconductivity has not yet been observed in known altermagnets, but many candidate materials are good metals, suggesting superconducting phases could emerge at low temperatures.
Why it matters: For spintronics researchers and low-power electronics designers, this theoretical work offers a route to spin-based information transport without the energy losses and stray-field interference that plague existing hybrid superconducting-magnetic systems. The make-or-break test: whether any of the "good metal" altermagnet candidates can actually be coaxed into a superconducting state at accessible temperatures.
