Below a temperature of 2.17 K, liquid ~4He undergoes a phase transition to a new state of matter with superfluid properties. It has long been accepted that a Bose-Einstein condensate is responsible, namely that a macroscopic number of atoms occupy the same quantum state. Direct evidence for this condensate has eluded our best efforts for many decades, but finally, as reported on page 56 of this issue by Wyatt, a macroscopic fraction of atoms with zero momentum has been observed in liquid ~4He. A Bose condensate of Cooper pairs also underlies superfluidity in superconductors and liquid ~3He.
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