Contemporary Physics Top 100 Dilemmas, Episode 88: the problem of strange metals and linear resistivity. Start with a material that refuses to behave. It has not yet become a superconductor, so current cannot run without loss. But it also refuses to act like an ordinary metal. In a familiar metal, electrons move through a lattice and bump into thermal vibrations, impurities, and defects. At low temperature, the resistance often follows a tidy T-squared pattern, like a highway with toll booths. In many materials related to high-temperature superconductors, however, the normal-state resistance rises almost linearly with temperature across a wide range. Raise the temperature by one step, and the resistance rises by almost one step, as if someone had drawn a ruler-straight slope on the graph. It can be hard to find clear, long-lived quasiparticles. Heat capacity, scattering time, and magnetotransport do not sit comfortably inside the textbook metal story. Then people talk about Planckian dissipation, as if the material itself is saying: stop treating me as a simple electron gas; my road network is no longer that kind of road. A strange metal is not a conventional metal, but it is not yet a superconductor either. It is like a city whose roads still exist and whose power grid is unfinished, while the traffic rules have already been rewritten. Mainstream physics is not empty-handed. One line points to quantum criticality: maybe the material sits near a phase transition, where fluctuations wash out quasiparticles. Another speaks of a marginal Fermi liquid, where electron lifetimes sit right on the edge. Others emphasize strong correlations, spin fluctuations, disorder, gauge fields, or even holographic models. Each route captures part of the scene. The hard part is why linear resistance is so stubborn, why it reappears across different material families, why it sits near the pseudogap and the superconducting dome, and why the ordinary T-squared metal rule is already broken before superconductivity has arrived. EFT begins by translating resistance. In EFT, conduction is not many charged beads flying through empty space. It is whether the shared corridor network inside the material can keep relaying a texture bias in an orderly way. Voltage writes a texture slope across the two ends of the sample. Current is the road network making a coordinated response to that slope. Resistance is the leakage rate from ordered circulation into disordered wave-packet channels. A bias that should pass cleanly through shared corridors is partly eaten by lattice vibration, defects, local polarization, and noise gates, then scattered into heat and messy little waves. Read this way, a strange metal is not one more mysterious metal species. It is a threshold-before-superconductivity transport zone. Local correlations have already rewritten many corridors, thresholds, and energy-leak doors, but the whole sample has not yet grown a fully locked common-phase network. Quasiparticles are like a convoy of cars. To exist clearly, the convoy needs stable lanes, stable speeds, and stable formation. In the strange metal, the road keeps shaking, the traffic lights keep changing, and the convoy is torn apart almost as soon as it forms. So the old language of sharp, long-lived quasiparticles loses its grip. Temperature also changes meaning here. In an ordinary metal, warming the sample is like making the road bumpier, so scattering gradually increases. In a strange metal, warming is more like opening rows of leakage gates one by one. The system is already standing near thresholds. Whether channels open, whether phases align, and whether local regions can dump energy are all sensitive to noise and boundary imprint. Each small rise in temperature pushes more critical little doors across their opening line. The fraction of ordered circulation leaking into disordered wave-packet channels then grows approximately in proportion to temperature, and the resistance naturally draws a line. Planckian dissipation, in this picture, need not first be mystified into a cosmic limit. It looks more like the emergency redline of this threshold road network: local beat, channel capacity, and the noise floor push energy loss to the roughest working ceiling, while a finer quasiparticle-lifetime ledger is no longer the right tool. This also explains why the strange-metal region lives so close to the pseudogap and the superconducting dome. They are not three unrelated rooms. They are three appearances of the same phase skeleton at different construction stages. If some low-energy channels are locally locked or swallowed first, the outside reads a pseudogap. If paired structures truly close, phase-lock, and join into a global lossless network, the outside reads superconductivity. The strange metal sits in the middle, like a city laying its main electrical grid: local lines have been rebuilt, old traffic rules have failed, but the whole city has not yet become one power system. One guardrail matters. EFT is not saying quantum criticality, strong correlation, or spin fluctuation ideas are useless. They may be local projections of this threshold zone. EFT is also not claiming final mathematics for every strange metal. Its move is to change the bottom-level grammar. Do not ask only how often electron beads collide. Ask whether shared corridors are connected, whether the phase skeleton has formed, how many leakage gates temperature opens, and how noise plus boundary imprint rewrites channels. The strangest thing about linear resistance is not only that it is ruler-straight. It is that it forces us to admit that some normal states are not normal metals at all. They are construction sites before superconductivity, ruled by thresholds, noise, leakage, and an unfinished phase network. Open the playlist for more. Next episode: the pseudogap phase in cuprates. Follow and share, and let this series of new-physics explainers help you see the universe more clearly.
EFT
Language