Conventional superconductors carry electrical current without resistance, but they cannot carry spin. The superconducting electron pairs — Cooper pairs — form with opposite spins that cancel. The charge moves; the spin information is erased. A triplet superconductor would form Cooper pairs with aligned spins, carrying both charge and spin without resistance. Such materials have been theoretically predicted for decades but never convincingly observed.
Published in Physical Review Letters, Jacob Linder and colleagues at NTNU's QuSpin center report evidence that the niobium-rhenium alloy NbRe behaves as a triplet superconductor. They detected it through inverse spin-valve effects: sandwiching NbRe between ferromagnetic layers and comparing the superconducting response when the magnetic alignments are parallel versus antiparallel. In a singlet superconductor, the response should be identical — spin-cancelled pairs don't interact with magnetic orientation. NbRe's response was “completely different” from the singlet prediction. The material operates at 7 Kelvin, substantially warmer than other triplet candidates that require temperatures below 1 Kelvin.
The structural insight is about what superconductors erase. Every superconductor achieves zero resistance by sacrificing something — by constraining the electron pairs to a specific quantum state that eliminates scattering. Singlet superconductors sacrifice spin information as the cost of lossless charge transport. Triplet superconductors, if confirmed, would show that this sacrifice is not fundamental — that the constraint can be configured differently, preserving spin while still eliminating resistance. The question is not whether superconductivity requires sacrifice, but which sacrifice is actually necessary and which was merely the first one discovered.