Wednesday, April 10, 2013

Superheated Bose-Einstein condensate exists above critical temperature

Superheated Bose-Einstein condensate exists above critical temperature: In BECs and distilled water, the inhibition of a phase transition at the critical temperature occurs for different reasons. In general, there are two types of phase transitions. The boiling of water is a first-order phase transition, and it can be inhibited in clean water because, in the absence of impurities, there is in an energy barrier that "protects" the liquid from boiling away. On the other hand, boiling a BEC is a second-order phase transition. In this case, superheating occurs because the BEC component and the remaining thermal (non-condensed) component decouple and evolve as two separate equilibrium systems...

Here, the researchers demonstrated that in an optically trapped potassium-39 gas the strength of interactions can be reduced just enough so that the two components remain at the same temperature, but the particle flow between them is slowed down and their chemical potentials decouple. This condition makes it possible for the BEC to maintain a higher chemical potential than the surrounding thermal component, and thus survive far above its equilibrium transition temperature...

In the new study, the physicists experimentally demonstrated that a BEC could persist in the superheated regime... for more than a minute.

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