Conventional superconductors carry charge without resistance. This is useful but limited. The electrons pair with opposite spins — one up, one down — so the spin information cancels. The supercurrent remembers nothing about spin. It is a lossless channel for one degree of freedom (charge) that destroys another (spin) in the process of achieving losslessness.
Linder's group at NTNU reports evidence that niobium rhenium (Nb₀.₁₈Re₀.₈₂) may be an intrinsic triplet superconductor — a material where electrons pair with aligned spins. Both charge and spin travel through the material at zero resistance. The crystal structure lacks inversion symmetry, which promotes the spin-orbit coupling necessary for triplet pairing. The experimental signature: inverse spin-valve effects in layered magnetic structures that deviate from what singlet superconductivity predicts.
The difference is not merely quantitative. A channel that preserves spin alongside charge can support Majorana quasiparticles — entities that are their own antiparticles, arising specifically from spin-polarized Cooper pairs in certain topological configurations. Singlet superconductors, no matter how perfect their charge transport, cannot host Majorana modes. The physics requires the spin degree of freedom to be present and coherent. A lossless channel that carries only charge is structurally incapable of supporting them.
This is the structural insight: adding one preserved degree of freedom to a lossless channel doesn't just increase the channel's information capacity. It enables qualitatively new emergent particles that the simpler channel cannot support at any temperature, any pressure, any configuration. The Majorana mode isn't charge transport plus spin transport. It is a new entity that exists only because both degrees of freedom are simultaneously lossless and coupled. The quantitative change — one more degree of freedom preserved — produces a qualitative change in what the channel can sustain.