Rails for superconductor vortices: atomic steps guide magnetic flux vortices
Researchers in Japan show that steps just one atom high in an ultrathin superconductor guide magnetic vortices like rails – along the steps they move more than 1,000 times more easily.
Archive image · Photo: Syced / Wikimedia Commons, CC0 (cropped and resized)
A team led by Takashi Uchihashi at the MANA research centre of Japan's National Institute for Materials Science (NIMS) has studied an ultrathin superconductor whose surface features regularly spaced steps just one atom high. The results were published in the journal Physical Review B (vol. 114, issue 5; DOI 10.1103/b2j3-xj19); ScienceDaily reported on them on 16 October.
Magnetic fields penetrate superconductors in the form of tiny vortices; when they move, they can generate electrical resistance. In the material studied, the vortices – here so-called Josephson vortices – lined up along the steps, as scanning tunnelling microscope images showed. Under intermediate magnetic fields they moved more than 1,000 times more easily along the steps than across them; between about 0.10 and 0.20 tesla they flowed without getting trapped by material defects. At the lowest temperatures, quantum tunnelling governed their motion.
According to Uchihashi, the guiding effect can be tuned simply by changing the temperature or magnetic field. In the long run this could help make superconducting electronics more energy-efficient and allow targeted control of vortex motion and heat flow in devices. However, the release notes that further development is needed before practical applications.