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Cornell University
LASSP -  Laboratory of Atomic and Solid State Physics

Cornell Laboratory for Atomic and Solid State Physics

Visualizing how radiation bombardment boosts superconductivity

A precision spectroscopic-imaging scanning tunneling microscope (SI-STM) developed by Davis is the first tool that can map out those three characteristics on the same material. Under Davis' guidance, Brookhaven Lab postdoctoral fellow Freek Massee (now at University Paris-Sud in France) and Cornell University graduate student Peter Sprau -- the two lead co-authors on the paper -- used the instrument's fine electron-tunneling tip to scan over the material's surface, imaging the atomic structure of the landscape below and the properties of its electrons, atom by atom. The precision allows the scientists to scan the same atoms repeatedly under different external conditions -- such as changes in temperature and ramped up magnetic fields -- to study the formation, movement, and effects of quantum vortices.

Their atomic-scale imaging studies reveal that vortex pinning -- the ability to keep those disruptive eddies in place -- depends on the shape of the high-energy ion damage tracks (specifically whether they are point-like or elongated), and also on a form of "collateral damage" discovered by the researchers far from the primary route traversed by each ion. Collaborating theorists at the University of Illinois are now using the experimental results to develop a descriptive framework the scientists can use to predict and test new approaches for materials design.

"These studies will really help us solve at which temperature which type of defects will be best for carrying a particular current," Kwok said. "The ability to achieve critical current by design is one of the ultimate goals of the Center for Emergent Superconductivity."

 

High-energy gold ions impact the crystal surface from above at the sites indicated schematically by dashed circles.