A superconductor is a material that conducts electricity without loss, but only below a certain temperature, called the critical temperature. The higher this temperature, the easier it is to use the superconductor in technology. For decades, scientists have searched for materials with high critical temperatures, but often they worked blindly, like treasure hunters without a map.
In this work, the map was drawn in a new way. They took thousands of known superconductors, described each with many numbers, and looked at how they arrange themselves. It turned out that three different families—cuprates, iron pnictides, and nickelates—cluster together. It is as if three expeditions, searching for treasure in different places, independently arrived at the same cove.
Now any new material can be checked to see if it falls into this cove, and its critical temperature can be estimated. The authors have already found several candidates worth trying to synthesize in the lab. The map does not explain why superconductivity arises, but it provides a compass for the search.
Matthias's rules, formulated in the 1950s, stated that good superconductors have on average 5 or 7 valence electrons per atom. The new analysis finds an optimum in the range of 7–8, which is surprisingly close to the old empirical rule, but now backed by machine learning on thousands of compounds.
In Arthur C. Clarke's novel 'Childhood's End', room-temperature superconductors transform the energy and transportation of an entire civilization. The search for such materials in reality often proceeds blindly; this work offers a compass that could bring science fiction closer to the laboratory bench.