Imagine a line of people holding hands but facing in opposite directions: some look north, others south. That's how a p-wave magnet is arranged. Electrons in it align their magnetic moments (spins) not randomly but in a strict wave-like pattern. This pattern, on its own, without heavy atoms or relativistic effects, splits the energy levels for electrons with different spin directions, as if, in that line, the people facing north were slightly taller. This splitting is called nonrelativistic spin splitting. The authors found that it can give rise to superconductivity with unusual properties.
When electrons in such a magnet start attracting each other (for instance, due to crystal lattice vibrations), they form pairs — Cooper pairs, the carriers of superconducting current. But because the spins in a pair are no longer equivalent, a mixture of two types of pairs emerges: singlet pairs, where spins point in opposite directions, and triplet pairs, where they are aligned. In a conventional superconductor, these types do not mix. Here, the magnetic pattern forces them to coexist in the same channel, like in a dance where partners perform both waltz and tango simultaneously. The dominant state is one where the triplet part is rigidly tied to the axis of the exchange field — scientists call it the Ising mixed-parity state.
Then comes the most interesting part. If you increase the attraction between neighboring atoms, the superconducting state changes: nodes appear — points on the Fermi surface where the binding energy drops to zero. This phase becomes topological. At the sample's edge, Majorana modes emerge — exotic excitations that behave like half-electrons. They are protected from disturbances not by an energy gap but by topology itself: locally, they cannot be destroyed without changing the system's global properties. These modes 'live' on specific parts of the edge, exactly under the directions where nodes gape in the bulk. Adding an external magnetic field perpendicular to the internal one can yield another type of topological phase: this time with protection described by the number 0 or 1 (the so-called Z₂ phase).
The practical takeaway: p-wave magnets could become a testing ground for creating and studying topological superconductivity without the need for expensive and complex materials with strong spin-orbit coupling. This is a step toward quantum computers where information would be stored in entangled Majorana states, almost insensitive to the jitter of the outside world, like an inscription carved in stone compared to ink on paper.
In p-wave magnets, electron spins align so that their spatial distribution resembles a wave with alternating crests and troughs — hence the letter p, as in the atomic p-orbital.