Atomic-scale “Rails” guide superconducting vortices in ultrathin materials

Researchers at the Research Center for Materials Nanoarchitectonics (MANA), part of Japan’s National Institute for Materials Science (NIMS), have discovered that single-atom-high surface steps on ultrathin superconductors can act as directional “rails” for superconducting vortices

Published in Physical Review B, the study demonstrates that these atomic steps allow quantum vortices to move more than 1,000 times more easily along the steps than across them, enabling tunable one-dimensional vortex flow that could advance ultralow-power quantum and electronic devices.

Controlling quantum vortices at the nanoscale

In two-dimensional, ultrathin superconductors, magnetic fields penetrate the material in the form of quantised magnetic flux tubes known as superconducting vortices. The uncontrolled movement or pinning of these vortices dissipates energy and disrupts superconducting states.

Controlling vortex motion is critical for improving heat dissipation and processing efficiency in next-generation superconducting electronics, yet directional control in 2D systems has historically proven difficult.

Led by Dr Takashi Uchihashi, the MANA/NIMS research team synthesised an atomic-layer superconductor on a vicinal surface featuring parallel, regularly arranged single-atom surface steps. Using scanning tunnelling microscopy (STM), the team directly visualised individual vortices aligned along these microscopic step edges.

Transport anisotropy and quantum tunnelling mechanics

Through four-terminal electrical resistance measurements, the researchers analysed how magnetic fields and temperature influence vortex dynamics:

1. Massive transport anisotropy:

   • At intermediate magnetic fields, vortices encountered over 1,000 times less resistance when moving parallel to the atomic steps than when moving perpendicular to them.

2. Pinning-free 1D flow zone:

   • In magnetic fields ranging between approximately 0.10 T and 0.20 T, vortices flowed completely unhindered along the atomic step “rails” without experiencing typical defect pinning.

3. Tunable mechanics:

   • At the lowest temperature regimes, vortex transport transitioned from thermally activated motion to quantum tunnelling along the steps. The overall guiding efficiency could be dynamically tuned by altering external magnetic fields and temperature.

Technological potential

By proving that a one-atom-high structural step can channel vortex motion into a frictionless, one-dimensional corridor, the study establishes a practical method for manipulating magnetic flux and localised heat flow in nanoscale superconducting circuits. This directional control provides a foundational building block for future ultralow-power computation and high-efficiency quantum information processing technologies.