Guiding Quantum Vortices Along One-Atom-High Steps in Ultrathin Superconductors

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Discovery and Publication of Atomic-Scale Vortex Rails

A research team led by Takashi Uchihashi at the Research Center for Materials Nanoarchitectonics (MANA), within Japan's National Institute for Materials Science (NIMS), has identified that atomic steps just one atom high on the surface of an ultrathin superconductor can act as rails to guide the directional motion of quantum vortices. The team's findings were published in Physical Review B on July 30, 2026.

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Direct Observation via Scanning Tunneling Microscopy

The researchers confirmed the surface morphology and vortex behavior using scanning tunneling microscopy. This imaging technique allowed the team to confirm the presence of parallel atomic steps and directly visualize quantum vortices situated along them.

Directional Mobility and Pinning-Free Flow

Using four-terminal resistance measurements, the study revealed that quantum vortices moved more than 1,000 times more easily along the atomic steps than across them at intermediate magnetic fields. Between magnetic fields of approximately 0.10 and 0.20 T, the vortices flowed freely along the steps without hindrance from pinning, resulting in one-dimensional pinning-free vortex flow.

Tunability and Low-Temperature Quantum Tunneling

The guiding effect on the vortices can be tuned by altering the surrounding temperature or magnetic field. In addition, the researchers found that at the lowest temperatures, the motion of the vortices along the atomic steps was governed by quantum tunneling.