An ordinary superconductor expels magnetic fields, but this ring does the opposite: it creates a magnetic field inside itself. The ring is made of Fe(Te,Se) — a compound of iron, tellurium, and selenium that loses its electrical resistance at very low temperatures. When a current is passed through the ring, the electrons inside move in a coordinated way, and their spins — tiny magnetic moments — align in one direction. This gives rise to a magnetic field of its own, which can be measured.
The strength of this field grows in direct proportion to the current: more current means a stronger magnet. But the most interesting part is that the field's direction depends on both the magnitude and the polarity of the current. If the current flows one way, the field points up; if it flows the other way, it points down. And the dependence is not simple: at larger currents, the orientation can suddenly flip. It's like a switch that you can twist in different directions, and it clicks differently each time.
To explain this, the authors proposed a model involving the so-called Rashba interaction — an effect that occurs at the surfaces of materials, where electrons feel an electric field. Together with an anisotropic interaction that depends on direction, this produces the observed behavior. Such rings could become the basis for superconducting spintronics — electronics where information is encoded not by charge but by electron spin. This promises faster and more energy-efficient devices.
Superconductivity was discovered in 1911, when mercury was cooled to 4 kelvin — colder than outer space.
In Peter Watts's novel 'Maelstrom', superconductors are used to store information in quantum states.