Steps just one atom high on the surface of an ultrathin superconductor can steer magnetic vortices like rails, and the effect is large. Under certain conditions, the vortices moved more than 1,000 times more easily along the steps than across them, according to a team at Japan’s National Institute for Materials Science led by Takashi Uchihashi. The work was published in Physical Review B in 2026.
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Vortices and why they cost energy
A superconductor carries current without resistance, but a magnetic field can break that perfection. Where the field penetrates the material it does so as vortices, tiny whirlpools of current, and their motion can generate electrical resistance. Anything that controls where the vortices go therefore matters for devices that depend on resistance-free flow, which is why a surface feature that guides them draws attention from people who build superconducting electronics.
The material in this study is an atomic-layer superconductor on what physicists call a vicinal surface, one that has regularly spaced, parallel atomic steps. Each step is one atom high, so the landscape the vortices cross is a staircase on the smallest scale a solid can have. The paper’s title calls the objects that move along it Josephson vortices, and its central measurement is how easily they travel in two directions: along the staircase edges and across them. Pinning, in which vortices are held in place, is the effect the institute says is absent along the steps in the field range it studied. That combination of free motion in one direction and resistance to it in the other is what makes the surface a candidate for steering vortices on purpose, and it is the reason the researchers describe the steps as guides rather than as obstacles.
Steps one atom high as microscopic railroad tracks
According to the research highlight from the Research Center for Materials Nanoarchitectonics, known as MANA, scanning tunneling microscopy confirmed that the steps ran parallel and showed vortices located along them. The team then measured the resistance with four terminals and found the large directional difference at intermediate magnetic fields. In a field of about 0.10 to 0.20 tesla, vortices flowed along the steps without being held in place by pinning, a condition the institute calls one-dimensional pinning-free vortex flow.
Uchihashi’s own summary is short: atomic-scale steps can act as effective rails that guide superconducting vortices. The institute’s page reaches for the same image, describing steps one atom high as microscopic railroad tracks, and the comparison fits the numbers. A vortex that moves more than 1,000 times more easily in one direction than in the perpendicular one is, for practical purposes, confined to a track, which is what the measurements of four-terminal resistance indicate at the intermediate fields.
Tunable by temperature and field
The guiding effect is not fixed. Uchihashi said it can be tuned simply by changing the temperature or the magnetic field, which is the property that would make the steps useful rather than just interesting. ScienceDaily’s account of the study adds that at the lowest temperatures vortex motion is governed by quantum tunneling, a quantum effect in which a vortex can pass through a barrier rather than climbing over it. Neither the institute’s page nor ScienceDaily names the superconductor or the substrate, and neither gives specific temperature values, so the 1,000-fold figure should be read as the result for the conditions the team reported rather than as a general property of every stepped surface.
The team behind the work spans institutions and countries. Wenxuan Qian, Ryohei Nemoto, Keisuke Sagisaka and Shunsuke Yoshizawa worked with Uchihashi at MANA, and Yash Chauhan came from the National Institute of Science Education and Research in India. Qian, Nemoto and Uchihashi also hold affiliations at Hokkaido University or the Institute of Science Tokyo, and Chauhan is affiliated with the Homi Bhabha National Institute, according to the author list on the institute’s page.
Where the finding stands
The paper, titled “Anisotropic transport of Josephson vortices in atomic-layer superconductors on vicinal surfaces,” was published in Physical Review B, volume 114, issue 5, on July 30, 2026, according to the institute; the journal’s own record is its abstract page at the American Physical Society, and a separate entry for it sits in the institute’s materials data repository. The word anisotropic in the paper’s name is the technical statement of the main result: the same vortices behave very differently depending on whether they travel along the steps or across them.
The finding is a laboratory result about a specific kind of sample, and the sources are explicit about the distance between that and a device. Neither the institute nor ScienceDaily describes a working circuit, a voltage or a heat-flow measurement made with the steps in place, and the claims about future technology are framed as possibilities. What the study establishes is the direction-dependent flow itself, observed with a microscope that could see the vortices sitting along the steps and with resistance measurements that quantified how freely they moved.
The applications MANA names are ultralow-power superconducting technologies, in which controlling the direction of vortex motion may matter, and better management of vortex motion and heat flow in future devices. The institute and ScienceDaily both stress that practical applications will need further development. A Quantum Insider write-up from Sept. 26 covers the same result.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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