A nanowire that contains just four molecules can be superconducting, according to research published online in Nature Nanotechnology this week. This work helps to better understand superconductivity and the materials involved.

When a superconductor is cooled below a certain temperature it is able to conduct electricity without losing any energy as heat, which is why some researchers are trying to make longer superconducting wires. However, other researchers are trying to make smaller superconducting structures, so that they can learn more about these materials.

Saw-Wai Hla and co-workers deposited molecules of an organic charge-transfer salt on a silver surface and used a technique called scanning tunnelling spectroscopy to examine the molecular islands and chains that formed on the surface. They found evidence for a superconducting gap ― a classic signature of superconductivity ― at temperatures within ten degrees of absolute zero. The size of this gap depended on the length of the chains, and the gap could still be seen in wires that contained just four molecules.