Researchers have made the first direct visual observation and measurement of ultra-fast vortex dynamics in superconductors. Their technique, detailed in the journal Nature Communications, could contribute to the development of novel practical applications by optimizing superconductor properties for use in electronics.
An international team of researchers, led by Prof. Eli Zeldov from the Weizmann Institute of Science and Dr. Yonathan Anahory, senior lecturer at the Hebrew University of Jerusalem’s Racah Institute of Physics, has shown for the first time how these vortices move in superconducting materials and how fast they may travel.
They used a novel microscopy technique called scanning SQUID-on-tip, which allows magnetic imaging at unprecedented high resolution (about 50 nm) and magnetic sensitivity. The technique was developed over the last decade at the Weizmann Institute by a large team including Ph.D. student Lior Embon and Ella Lachman and is currently being implemented at the Hebrew University in Dr. Anahory’s lab as well.
Using this microscope, they observed vortices flowing through a thin superconducting film at rates of tens of GHz, and traveling at velocities much faster than previously thought possible — up to about 72 000 km/hr.
This is not only much faster than the speed of sound, but also exceeds the pair-breaking speed limit of superconducting condensate
In photos and videos shown for the first time, the vortex trajectories appear as smeared lines crossing from one side of the film to another. This is similar to the blurring of images in photographs of fast-moving objects. They show a tree-like structure with a single stem that undergoes a series of bifurcations into branches. This channel flow is quite surprising since vortices normally repel each other and try to spread out as much as possible.
Here vortices tend to follow each other, which generates the tree-like structure.