The surface of the uranium compound UTe2 crystal looks like a frozen sea: in some places, electrons move freely; in others, they get stuck near atoms. A scanning tunneling microscope, a device that probes the surface with an atomically sharp tip and senses individual electrons, revealed that this landscape is not random. A regular ripple emerged: a wave in which magnetic moments and conduction electrons occupy positions in turn, like squares on a chessboard.
This wave is called the Kondo hybridization wave. Hybridization is when two different states mix into a single new one. Here, heavy electrons (those sitting on uranium atoms) mix with light conduction electrons. Previously, it was thought that this mixing occurs smoothly, without clear order. Now it is clear that at low temperatures, it arranges itself into a periodic structure.
Superconductivity, a state in which current flows without resistance, exists alongside this ripple. In the uranium compound, superconductivity is unusual: the electron pairs that create it spin in the same direction, like figure skaters in pair skating. The new wave may explain how such pairs form. This is important because resistance-free superconductors could transmit energy without losses, but so far they only work at very low temperatures.
The discovery shows that in strongly interacting systems, order can hide where it is least expected. The wave on the uranium crystal's surface is like a pattern emerging on frosted glass: it was always there, but only now have we been able to see it.
The uranium in UTe2 is the same element used in nuclear fuel, but here it acts as a magnetic player, not an energy source.