Current in an ordinary metal flows like a crowd of people down a straight street: each electron is on its own, and if you turn on a magnetic field, the whole crowd shifts slightly sideways. This shift is called the Hall effect. But in 'strange metals'—materials where electrons behave not as individual particles but as a single whole — the picture breaks down.
In the study, they investigated the superconductor BaFe2(As1-xPx)2, varying the phosphorus fraction x. Above the quantum critical point, a special state where the material ceases to be magnetically ordered, they found a contribution to the Hall effect that does not depend on x. It resembles the response of an antiferromagnet but has universal features: it is not related to a restructuring of the Fermi surface (that 'street' along which electrons run).
This 'Hall contribution of the strange metal' points to a common source: quantum fluctuations, which also explain the linear increase of resistance with temperature and the emergence of unconventional superconductivity. Thus, different strangenesses come together into one picture.
The bottom line: in a strange metal, a universal contribution to the Hall effect has been found that does not depend on composition and is related to quantum fluctuations. This is a step toward understanding why such materials conduct electricity so well without familiar particles.
Strange metals got their name for the linear increase of resistance with temperature — in ordinary metals it is quadratic.
In science fiction, 'strange metals' could become the basis for superconductors operating at room temperature — for now, that's just a dream.