Researchers at Japan’s National Institute for Materials Science have identified a novel method for controlling quantum vortices in ultrathin superconductors using atomic-scale surface features. The team, led by Takashi Uchihashi at the Research Center for Materials Nanoarchitectonics, found that regularly spaced steps just one atom high can act as guidepaths for these quantum structures, dramatically facilitating their movement in specific directions.
Superconductors are materials capable of conducting electricity without resistance when cooled below a critical temperature. However, they contain quantum vortices that form where magnetic fields penetrate the material, creating regions of circulating electrical currents. When vortices move, they generate electrical resistance and degrade superconductor performance. The ability to direct vortex movement, particularly in two-dimensional superconductors, has presented significant challenges for researchers seeking to improve device efficiency.
The study examined an ultrathin superconductor with a series of parallel atomic steps on its surface. Using scanning tunneling microscopy to image surfaces at atomic resolution, researchers confirmed vortex positioning along these steps. Four-terminal resistance measurements revealed that vortices traveled more than 1,000 times more readily along the atomic steps compared to perpendicular directions when exposed to intermediate magnetic fields. This directional preference creates what researchers describe as microscopic rails for quantum motion.
The research identified a particularly significant behavior within a magnetic field range of approximately 0.10 to 0.20 tesla, where vortices could flow freely along the steps without becoming trapped by material imperfections. The findings indicate that temperature and magnetic field adjustments can tune this guiding effect. At the lowest temperatures, vortex motion became governed by quantum tunneling, allowing particles to pass through energy barriers that would normally restrict movement.
The discovery, published in Physical Review B, suggests that even minimal surface features can substantially influence quantum vortex behavior. The researchers indicate this atomic-scale approach could enable better management of vortex movement and heat flow in future superconducting technologies, potentially supporting the development of more energy-efficient devices with reduced power consumption.
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