Tokyo researchers prove clogging is a phase transition using superconducting vortices

Study confirms long-standing prediction

Takahide Minemura, a former graduate student, and professor emeritus Satoshi Okuma headed a group that studied how direct current drives the critical dynamics of superconducting vortices. Their work, published in Communications Physics on Sept. 25, 2026, provided the first experimental verification that clogging represents a nonequilibrium phase transition. Previous simulations predicted this behavior, but experimental confirmation had remained elusive for years. The team successfully distinguished this specific phenomenon from conventional pinning effects observed in similar materials.

New measurement protocol used

Scientists examined vortices moving through amorphous molybdenum-germanium thin films where material defects served as pinning sites. Researchers created an adjusted two-step measurement method using sequential current drives applied either in parallel or opposing directions. By measuring time-dependent voltage, they tracked vortex motion and separated fast relaxation associated with clogging from slower relaxation linked to pinning. The two relaxation periods grew significantly and followed a power-law divergence when the driving current neared a critical threshold.

Critical points coincide exactly

Experimental data showed that the current required to cause clogging matched the depinning current in the setup. These results provide fresh perspectives on forecasting and managing blockage in varied setups, spanning industrial pipes to biological circuits. Okuma noted that understanding these mechanisms is essential for preventing blockages in infrastructure and blood vessels. This research tackles an enduring inquiry about the physical processes controlling the shift from steady flow to total blockage.