Researchers from the University of British Columbia, Max Planck Institute for Solid State Research and University of Nevada have proposed a new class of quantum materials - superconducting altermagnets - that could carry persistent spin-polarized currents with zero dissipation, marking a potential breakthrough in superconducting spintronics.
The team's theoretical study shows how these materials can host spin supercurrents that remain stable even in the presence of spin-orbit coupling (SOC) and magnetic disorder - conditions that usually extinguish spin transport in normal metals.
In conventional superconductors, Cooper pairs are composed of electrons with opposite spins, leading to a single, charge-carrying condensate. By contrast, the team shows that superconducting altermagnets form two independent condensates - one from spin-up electrons and one from spin-down. In the nonrelativistic limit, where spin–orbit coupling is negligible, these two fluids are completely decoupled, allowing them to flow independently.
This independent behavior enables a remarkable effect. When the spin-up and spin-down supercurrents flow in opposite directions, their charge contributions cancel while their spin contributions reinforce, resulting in a pure spin supercurrent that transports angular momentum without any accompanying charge flow. The researchers call this the “spin-current dynamo effect”, showing that applying a conventional charge current along certain crystallographic directions can spontaneously generate a transverse spin supercurrent.
Unlike spin currents in normal metals and semiconductors, which usually decay within nanometers due to spin relaxation, the predicted spin supercurrents in superconducting altermagnets show no measurable decay. Even when SOC and magnetic impurities are included, the spin current merely develops spatial oscillations but remains nondissipative over arbitrary distances. This persistence stems from the fact that the spin-supercurrent state already minimizes the system’s free energy, leaving no mechanism for energy loss.
Superconducting altermagnets may also overcome key limitations of existing proximity-based superconducting spintronic devices. Earlier architectures often rely on multilayer heterostructures - sometimes with a dozen precisely engineered layers - to sustain spin-polarized supercurrents. In contrast, a single-layer altermagnet could, in principle, achieve similar functionality. Because altermagnets exhibit zero net magnetization, they produce no stray magnetic fields, reducing magnetic interference between nearby device elements.
Although intrinsic superconductivity in altermagnets has not yet been observed experimentally, many members of this family are good conductors, and theory suggests that a conventional phonon-mediated pairing mechanism could drive the expected spin-triplet p-wave superconductivity at low temperatures. The researchers emphasize that this triplet state arises naturally from the spin-split band structure of altermagnets, without requiring exotic interactions.
If realized in materials form, superconducting altermagnets could enable persistent, dissipationless spin transport - a key goal of spintronics. By merging magnetism’s spin control with superconductivity’s perfect conductivity, they could pave the way for ultra-efficient, stray-field-free spintronic circuits, offering a fundamentally new platform for quantum technologies.