Bose-Einstein Condensate

A Bose-Einstein condensate is a new form of matter made at the coldest temperatures in the universe. Essentially the condensate is a collection of identical atoms behaving as one entity. How do the individual atoms lose their self-identity?

Answer

A Bose-Einstein condensate is formed at the coldest temperatures, which means that the atoms have been slowed in their motion to be almost stationary. By the de Broglie relation, each atom of mass m has a de Broglie wavelength λ = h/p, where p is its momentum mv and h is Planck’s constant. As the velocity v is further reduced to cool the atoms, the de Broglie wavelength increases accordingly. Eventually temperatures are reached for which the wavelengths of adjacent and nearby atoms begin to overlap in space considerably. Further cooling places all the atoms in intimate contact in one collective quantum state. Individual atoms can no longer be discerned because they act like one big “atom.”

The first Bose-Einstein condensate was achieved in 1995, even though the physics principles have been known since Einstein and Bose proposed them in the 1920s. About 2000 rubidium atoms in the gas were cooled to 170 nanoK when they formed a Bose-Einstein condensate less than 100 micrometers across. The condensate lasted for about 15 seconds and was cooled further, all the way down to 20 nanoK.