Researchers in Japan have discovered that single-atom-high surface steps on ultrathin superconductors function as directional rails, allowing quantum vortices to move more than 1,000 times more easily along the steps than across them and enabling tunable one-dimensional flow that could advance future electronics.
Working at the Research Center for Materials Nanoarchitectonics, part of Japan’s National Institute for Materials Science, a scientific team investigated how magnetic fields penetrate ultrathin superconductors. In these two-dimensional materials, magnetic flux enters as quantized flux tubes known as superconducting vortices. Uncontrolled movement or pinning of these vortices causes energy dissipation and disrupts superconducting states, making directional control a persistent challenge for next-generation electronics.
Scanning Tunneling Microscopy and Vicinal Surface Preparation
To overcome historical difficulties in controlling vortex direction in 2D systems, the team led by Dr Takashi Uchihashi synthesised an atomic-layer superconductor on a vicinal surface featuring parallel, regularly arranged single-atom surface steps. Using scanning tunneling microscopy, the researchers directly visualized individual vortices aligned neatly along these microscopic step edges, confirming the physical structure that guides them.
The findings, documenting what researchers titled Anisotropic transport of Josephson vortices in atomic-layer superconductors on vicinal surfaces
, were published in Physical Review B. The microscopy work verified that these microscopic step edges can steer quantum objects in a predictable manner, establishing a physical foundation for manipulating magnetic flux at the nanoscale.
Transport Anisotropy and Pinning-Free Quantum Flow
Through four-terminal electrical resistance measurements, the team analyzed how external magnetic fields and temperature shaped vortex dynamics. The tests revealed massive transport anisotropy across the material. When moving parallel to the atomic steps at intermediate magnetic fields, vortices experienced a reduction in resistance of more than 1,000-fold compared to movement in the perpendicular direction.
Within magnetic fields spanning roughly from 0.10 T to 0.20 T, vortices traveled smoothly along the atomic step rails, bypassing standard defect pinning and forming a one-dimensional flow zone free of pinning. At the lowest temperature regimes, vortex transport shifted from thermally activated motion to quantum tunneling along the steps, with overall guiding efficiency dynamically adjustable via external fields and thermal changes.
Implications for Nanoscale Superconducting Circuits
By proving that a one-atom-high structural step can channel vortex motion into a frictionless corridor, the research establishes a practical method for manipulating magnetic flux and localized heat flow. This capability for directional guidance serves as an essential stepping stone for advanced quantum information processing platforms and upcoming ultralow-power computational systems.
