A sheet less than a nanometer wide and four pairs of molecules now constitutes the world’s smallest superconductor and proves that superconducting nanoscale materials can be made, an obvious advance for nano-scaled electronics and energy applications.
Until now it has been thought that you couldn’t possibly use metallic conductors to link circuits at nanoscale levels, because the conductors’ resistance increases as the size of the wires becomes smaller, and they could become so hot that they would “fry” in a split second. Using superconductors, though, changes things radically.
Superconductors have a resistance close to zero, and thus their Joule heating effect doesn’t apply in the same manner it applies to normal conductors. The current finding suggests that superconductivity can exist at the molecular scale, after science thought for almost a hundred years that it would only exist at macro scales.
Associate Professor Saw-Wai Hla, from the University of Ohio, who led the study, used a type of organic salt, (BETS)2-GaCl4, placed on a silver surface. Superconductivity was observed in this material at molecular levels by using scanning tunneling spectroscopy, in molecular chains of various lengths. The effect decreased below 50 nm, but the phenomenon still existed in chains as small as four pairs of molecules, having 3.5 nm in length.
The temperatures used had been as low as 10 degrees Kelvin – using higher values reduced the superconductive activity. In the future, though, scientists will test different types of materials that could form nanoscale superconducting wires at higher temperatures.
“But we’ve opened up a new way to understand this phenomenon, which could lead to new materials that could be engineered to work at higher temperatures,” said Hla, adding that the process would be interesting for those seeking to make nanoscale electronic circuits using organic molecules.