The crystal of the uranium compound UTe2 resembles a layered cake where electrons flow without resistance. But if you examine its surface under a microscope, you see ripples, like waves on water from a thrown stone. These waves are not made of water but of electric charge: electrons bunch up and spread out, forming a periodic pattern.
Scientists cooled the sample, applied a magnetic field, and altered the crystal itself. It turned out that the pattern consists of several superimposed waves, all obeying strict rules: their wavelength is always a multiple of 1/14 or 1/4 of the distance between atoms. Such "locked" waves are not random: they are like piano keys that can only be pressed at specific spots.
The most interesting part: the waves neither enhance nor suppress superconductivity. This means they are not competitors but rather neighbors. Most likely, there is magnetic order on the surface of UTe2—electron spins align in a pattern like compass needles. It is this order that creates the charge ripples.
Such surface magnetic order is a rare guest in superconductors. It resembles a thin film of ice on a warm pond: fragile by itself, but it changes the reflection of light. Perhaps this "film" is responsible for the unusual properties of UTe2 that physicists have been trying to understand for several years.
A scanning tunneling microscope senses individual atoms: its tip approaches so closely that electrons "jump" across the gap, and the current can be used to map the surface.