Georgia Tech researchers, writing in the journal Science, report surprising behavior exhibited by nanometer-scale clusters of the metal niobium when they are cooled to below minus 424 degrees Fahrenheit.
I would not be surprised if the “nanometer-scale clusters” aspect of the investigation has some significant impact on the behavior. A surface represents a loss of symmetry present in a bulk material; surface effects are of interest to many physicists. A nanometer-scale cluster is going to have a fair amount of surface relative to its volume. So it’s probably not just that it’s cold.