Dopant atoms in superconductors attract electrons and leave the positively charged gaps that permit current flow without electrical resistance.
Dopants may also create electronic disorder at the atomic level. But to date, no one could resolve the atomic structure to confirm the correlation.
Now, a Cornell University team, using a scanning tunneling microscope, has mapped current flow in cuprate superconductor samples doped with different amounts of oxygen atoms. It turns out when dopant atoms are far away from the conducting plane, electron waves are homogeneous and the material superconducts. But the waves become heterogeneous and superconductivity ceases when dopant atoms sit near the conducting plane.
Molecular structure and how dopant atoms affect current flow in their immediate vicinity is key to understanding superconductor behavior say researchers. The stakes are high. Experts predict the worldwide market for superconductors will reach $5 billion by the year 2010.