The discovery came almost as an afterthought. In the mid-1980s, researchers racing to understand high-temperature superconductors in copper-oxide ceramics noticed something odd. When the materials were too warm to superconduct, they didn’t behave like normal metals either. Their electrical resistance rose in a perfectly straight line with temperature, no curvature, no plateau, no deviation. Forty years later, physicists are still trying to explain it.
“The conductor from Hell,” the late theorist Joseph Polchinski called it.
Normal metals follow a predictable pattern: as temperature drops, resistance falls as T², following the mathematics of electrons behaving like well-defined billiard-ball-like entities called quasiparticles. This picture, developed by Lev Landau in the 1950s, forms the foundation of modern electronics. “The entire electronics industry, including the iPhone in your pocket, is based on the success of this theory,” says Subir Sachdev, a Harvard theorist.
Strange metals break that foundation. Their resistance is proportional to temperature itself (R ∝ T), a linearity so stark and so persistent that it has defied explanation across four decades of experimental and theoretical work.
The shot-noise clue
The breakthrough came from a surprisingly simple measurement. In 2023, Doug Natelson’s group at Rice University fabricated nanowires of a heavy-fermion strange metal called YbRh₂Si₂ and measured its quantum charge fluctuations, the faint electrical crackle known as shot noise. When individual charges flow one by one through a conventional metal wire, the noise follows a predictable pattern with a Fano factor (noise-to-current ratio) of 1/3. In YbRh₂Si₂, the Fano factor was suppressed far below that.
“Maybe this is evidence that quasiparticles are not well-defined things or that they’re just not there, and charge moves in more complicated ways,” Natelson told New Scientist. “We have to find the right vocabulary to talk about how charge can move collectively.”
Theoretical work by Wang, Setty, Sur, Chen, Paschen, Natelson, and Qimiao Si (Phys. Rev. Research 6, L042045, 2024) showed that even a strongly correlated Fermi liquid should yield a Fano factor of √3/4, about 0.433. The observed suppression was significantly smaller, requiring an actual loss of quasiparticle identity.
The quantum soup picture
If electricity in strange metals is not carried by individual particle-like entities, what is it? The emerging picture is something closer to a quantum soup, a liquid-like flow of charge with no well-defined constituent parts. The YbRh₂Si₂ crystals for the shot-noise experiments, provided by Silke Paschen at TU Wien, changed her own mental model. “It’s actually something very controlled. It’s the silent place,” she said of the strange metal state.
Supporting evidence comes from multiple directions. In 2026, Stephen Hayden’s team at the University of Bristol used neutron beams at the Rutherford Appleton Laboratory to measure electron-spin fluctuations in a strange metal, finding that spin fluctuations speed up and slow down in lockstep with temperature, strong evidence for a fluctuation-based explanation of linear resistance. The work was published in Nature Communications with co-authors including Subir Sachdev.
Peter Abbamonte at the University of Illinois, who has studied charge density in strange metals with an electron gun, describes the behavior as bizarre: “There’s no measurement you can do with the system that tells you how many electrons are in it. They really just behave in a very bizarre way.”
The SYK connection
On the theoretical side, a curious model from the 1990s has become central. In 1993, Sachdev and Jinwu Ye modeled a simplified quantum dot where every electron connects to every other, no spatial structure, no geometry. The result: electrical disturbance decays at a rate proportional to temperature, despite having no particles or space as we normally understand them. The model was initially dismissed as a toy, until Alexei Kitaev at Caltech showed in 2015 that an almost identical model, now called the Sachdev-Ye-Kitaev (SYK) model, connects strange metal behavior to black hole physics through the holographic principle.
“It’s like the rug being pulled out from under our feet,” Sachdev said.
The SYK model makes a radical prediction: resistance rises linearly with temperature because current loses momentum at a rate that depends only on temperature and Planck’s constant, fundamental constants, not the material’s chemistry. If true, it means electricity in some materials is governed by a universal quantum speed limit, not by the familiar quasiparticle interactions that explain everything from copper wires to silicon chips.
What it means
Strange metals have now been observed in at least five different classes of materials: cuprates (1980s), iron pnictides (2009, by Louis Taillefer’s group), twisted graphene layers (2019, by Andrea Young and Cory Dean), nickelates (2023, by Harold Hwang’s group), and heavy-fermion compounds like YbRh₂Si₂. The phenomenon appears to be universal, independent of the specific chemistry, suggesting it reflects a fundamental principle of quantum matter rather than an exotic property of any particular material.
If the quasiparticle picture must be abandoned for these materials, the implications extend well beyond condensed matter physics. The SYK model’s connection to black hole thermodynamics and quantum gravity suggests that strange metals may be probing the same deep structure of quantum reality that physicists study with particle accelerators and gravitational wave detectors.
“It was the conductor from Hell,” Polchinski said. After 40 years, it may be the conductor that finally forces physics to rewrite the rules of electricity.
Sources
1. New Scientist, “The strange metals forcing us to rethink how electricity really works” (7 July 2026). https://www.newscientist.com/article/2531747-the-strange-metals-forcing-us-to-rethink-how-electricity-really-works/
2. Chen, L. et al., “Shot noise in a strange metal”, Science 382, 907-911 (2023). DOI: 10.1126/science.abq6100
3. Wang, C. et al., “Shot noise and universal Fano factor”, Phys. Rev. Research 6, L042045 (2024). DOI: 10.1103/PhysRevResearch.6.L042045
4. Radaelli, G. et al., “Critical spin fluctuations across the superconducting dome”, Nature Communications 17, 4564 (2026).
5. Sachdev, S. & Ye, J., “Universal quantum fluctuations in a strongly correlated system”, Phys. Rev. Lett. 70, 3339 (1993). DOI: 10.1103/PhysRevLett.70.3339