Plate Nº 21 · recorded November 12, 2026
PhysicsReported finding
Superconducting Vortices Prove Clogging Is a True Phase Transition
Science Tokyo researchers used superconducting vortices in MoGe films to give the first experimental proof that clogging is a nonequilibrium phase transition, published Sept. 25, 2026.
By Elena Vasquez3 min read646 words
In brief
- First experimental evidence that clogging is a nonequilibrium phase transition, published in Communications Physics on Sept. 25, 2026.
- Study led by Takahide Minemura and professor emeritus Satoshi Okuma at Institute of Science Tokyo.
- Clogging and depinning were found to share the same critical point within experimental uncertainty.
- Critical exponents matched the two-dimensional directed-percolation universality class.
- DOI: 10.1038/s42005-026-02880-5.
Researchers at Institute of Science Tokyo have delivered the first experimental proof that clogging — the moment flowing particles jam to a halt — is a genuine nonequilibrium phase transition. The study, published in Communications Physics on Sept. 25, 2026, ends a long wait. Simulations had predicted this transition for years, but no experiment had confirmed it.
The finding matters far beyond physics labs. Clogging shows up everywhere: granular materials, filtration devices, industrial pipelines, even blood vessels. Understanding exactly how smooth flow becomes a permanent blockage could help engineers and doctors anticipate and prevent it.
Why did this take so long?
A phase transition is a sharp change in a system's state — like water freezing into ice. A "nonequilibrium" one happens in systems driven by an external force, where the time needed to settle into a stable state — flowing or fully blocked — grows enormously near a critical point. Predicting that divergence is one thing. Measuring it is another. Experimental verification had simply remained elusive.
That gap motivated the Tokyo team, led by former graduate student Takahide Minemura and professor emeritus Satoshi Okuma of the Department of Physics.
"Clogging can also cause serious problems in industrial plants, infrastructure pipelines and biological transport systems such as blood vessels," Okuma said. "Although it has been predicted in simulation that the transition from a flowing state to a completely clogged state represents a nonequilibrium phase transition, experimental verification had remained elusive. This was the main motivation of our study."
How do you watch clogging happen?
The team worked with superconducting vortices — tiny whirlpools of magnetic flux that form inside superconductors, materials that carry current without resistance. They drove these vortices through amorphous molybdenum-germanium (MoGe) thin films using a direct current. Defects in the material acted as pinning sites that trapped vortices, and those trapped vortices formed bottlenecks blocking others. That's clogging, in miniature.
There was a catch. Clogging looks a lot like ordinary pinning, where defects simply grab vortices one by one. The researchers needed to tell the two apart.
Their solution was a modified two-step measurement protocol. They applied successive current drives in parallel, then in opposite directions, and tracked the time-dependent voltage that reported on vortex motion. The trick worked: clogging relaxes fast, while pinning relaxes slowly. The two signals separated cleanly.
What did they find?
The results landed with precision:
- Both relaxation times increased sharply as the driving current approached a critical value, following power-law divergence — the mathematical signature of a phase transition.
- The critical current for clogging coincided with the depinning current, the threshold at which vortices tear free of defects, within experimental uncertainty.
- The critical exponents — numbers that characterize how a transition behaves — matched predictions for the two-dimensional directed-percolation universality class, a known type of nonequilibrium absorbing phase transition.
In plain terms: clogging and depinning are distinct dynamical processes, but they share the same critical point and behave consistently at it. That's the core discovery.
Where does this lead?
The implications stretch well past superconductors. Okuma puts it directly: "Understanding, predicting and controlling clogging is important across scientific and engineering disciplines. The findings of our study may help guide future studies of flow obstruction in granular materials, colloids, active matter and other systems in which collective motion can become blocked."
Next steps could include testing how these critical dynamics change across different materials and transport environments. A deeper grasp of the flow-to-blockage transition could eventually sharpen strategies for managing clogs in industrial processes, infrastructure and biological transport networks.
Still, this is one experiment in one material system. Preliminary in the broad sense — the results are solid for vortex systems, and extending them to granular or biological contexts will take further work.
The paper is T. Minemura et al., "Clogging transition for vortices driven by dc current," Communications Physics (2026), DOI: 10.1038/s42005-026-02880-5.
via phys.org/rss-feed/ (Source)
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
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