Nature:
At low temperatures and high pressure, helium completely
solidifies, or does it? In 2004 Eun-Seong Kim and Moses Chan of
the Pennsylvania State University found evidence of a phase
within frozen He that appeared to flow through the solid like a
liquid. Since their experiment, the nature of "supersolidity"
has been unresolved: Is it a true many-body quantum phenomenon
or is it the result of imperfections in the solid?
Nature's Eugenie Samuel Reich reports on recent
experiments that might resolve the question.
