A type of quantum phase transition first predicted in 2013 has been seen by three independent teams of physicists. All three experiments involved systems of interacting ultracold atoms or ions and the observations could lead to a better understanding of the collective behaviour of quantum matter.
Phase transitions occur when matter transforms spontaneously from one state to another – from solid to liquid at the melting point of water, for example. Classical phase transitions are associated with thermal fluctuations in a system such as the random motion of water molecules. In contrast, quantum phase transitions involve fluctuations that arise from short-term changes in energy as described by Heisenberg's uncertainty principle. As a result, quantum phase transitions tend to occur at absolute zero or very low temperatures, where quantum fluctuations dominate over thermal fluctuations.
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