One of the outstanding mysteries of modern solid state physics is why certain materials conduct electricity without any energy losses at temperatures even above the boiling point of liquid nitrogen (at -196°C, colder than anywhere in nature). While still a rather low temperature compared to ambient conditions, it is an effect not captured by conventional wisdom. Researchers affiliated with the newly founded IMPP based at St Andrews and Stuttgart are working on solving this riddle since the discovery of the so-called high temperature superconductors 30 years ago.

 

From the beginning on, it was clear that superconductivity in these materials is driven by a mechanism different from the one in “normal” superconductors, where lattice vibrations have been identified as the enabler of superconductivity. Magnetism or better fluctuations of magnetic order appear to be a promising candidate for the unconventional superconductivity. A research team led by Dr Peter Wahl from the University of St Andrews has now achieved atomic-resolution imaging of the magnetic structure of a material which can be tuned into such an unconventional superconductor. Their tools are ultra-low temperature scanning tunneling microscopes which operate only a few hundreds of a degree above the absolute zero temperature. In these microscopes, the surface of the material is probed with a tip which hovers only a distance of a few atomic radii above the material. To enable magnetic imaging, the researchers had to apply a trick: rather than covering the tip with magnetic material, a technologically demanding process, they picked up some magnetic material from the surface – almost like a vacuum cleaner but with the magnetic material sticking to the end of the tip. This allowed the researchers to image the magnetic structure of the material at the atomic scale. With this novel approach, they now hope to shed new light into the mysteries of unconventional superconductivity, by being able to directly visualize both magnetic order and detect superconductivity in the same measurement.

Dr Wahl looks forward to pursue these studies in new cutting edge Ultra-low Vibration facility in St Andrews.

 

(M. Enayat, Z. Sun, U. R. Singh, R. Aluru, S. Schmaus, A. Yaresko, Y. Liu, C. Lin, V. Tsurkan, A. Loidl, J. Deisenhofer, P. Wahl, Real Space Imaging of the Atomic-Scale Magnetic Structure of Fe_1+yTe, Science 345, 653 (2014)).