Elusive ‘supersolid’ phase observed in experiments

In 1970 Nobel laureate Anthony Leggett made the apparently nonsensical suggestion that the properties of superfluid helium ‘may be shared by some solids’. Contradictory though it sounds the notion that a crystalline solid might flow like a superfluid – that is, having zero viscosity – without any compromise in rigidity has stuck, and the hunt has been on for such ‘supersolids’ ever since. Now Junsen Xiang at the Chinese Academy of Sciences in Beijing and researchers from China, France and Australia provide evidence for this elusive phase of matter. These supersolids may well be more than just a scientific curiosity and could be used to cool experiments and devices to close to absolute zero.