The wind carries pollen, and each grain moves as if on its own. But once the air swirls into a vortex, the pollen trajectories can no longer be separated: they are tangled. This is roughly how electrons behave in a strange metal: their motion is so strongly coupled to soft fluctuations of the medium that the usual particle carriers disappear.
Physicists built a model — a one-dimensional chain where electrons (two 'clouds' around special points) interact with a mediating field through random couplings. This is a simplified version of the so-called Yukawa-Sachdev-Ye-Kitaev model. When the mediating field becomes 'critical' (that is, ready for a sharp rearrangement), the system turns into a semblance of a strange metal. The main question was: how to measure quantum entanglement in such disorder?
The authors found a way to precisely compute this measure for any segment of the chain. And then a surprising picture emerged: entanglement between electrons and the mediating field within a single segment turned out to be no less important than entanglement between different segments. Both types of intertwining work together, and their combined contribution obeys a simple rule.
So the wind and pollen cease to be just a metaphor. In a strange metal, the medium does not merely hinder particles; it becomes their inseparable part. And the universal law of entanglement, found for a toy model, could be the very key that opens the door to understanding a whole class of mysterious materials — from high-temperature superconductors to the matter of neutron stars.
Strange metals got their name not for their exotic composition, but for their unusual behavior: their electrical resistance grows strictly proportionally to temperature, rather than according to familiar laws. This occurs in high-temperature superconductors and still lacks a full explanation.