Bose-Einstein Condensate

Vincent Dowling University of South Carolina

9/18/2015

History

. In 1924-1925, Bose wrote a paper on the quantum statistics for photons.

. Bose sent his paper to Einstein, who helped get it published and also applied the idea to non-interacting atoms. This formed Bose-Einstein Statistics.

. In 1995, the first gaseous condensate was made by Cornell, Wieman, and Ketterle

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What is Bose-Einstein Statistics

. It’s a way in which a group of indistinguishable particles that do not interact can occupy a set of discrete energy states. They must also be at thermodynamic equilibrium.

. Only works for particles that are not limited to only having one occupancy per state or in other words, particles that do not obey the Pauli Exclusion Principle.

. These particles are called Bosons.

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What is a BEC

. A BEC is a state of matter of a gas of bosons cooled to a temperature that is nearly absolute zero. A large majority of the bosons in this gas will occupy the lowest quantum state, allowing quantum phenomena to be apparent.

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What is a BEC

. The gas of bosons is cooled down. As the temperature is decreasing, the atoms slow down and the energy decreases.

. Because of their quantum nature, the atoms behave as waves and as the temperature gets even lower, the waves start to increase in size.

. At very low temperatures, the size of the waves becomes greater than the distance between the atoms.

. Eventually, the bosons will be in the same energy state and quantum state.

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What is a BEC

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What is a BEC

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2001 Nobel Prize

. Cornell and Wieman were awarded the 2001 Nobel prize in physics for their work in creating the first BEC.

. They used laser cooling and evaporative cooling in a magnetic trap on Rubidium 87 to create the BEC.

. They cooled it to 20nK when the condensate formed with about 2000 atoms remaining.

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2001 Nobel Prize

. Ketterle also received the 2001 Nobel prize, but he worked separately from Cornell and Wieman.

. Ketterle used sodium atoms and used the same process as Cornell and Wieman. However, he also focused a powerful laser beam in the center of the trap which held many more atoms in.

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2001 Nobel Prize

. With many more atoms to work with in the BEC, it allowed for measurements of the BEC.

. For example, it was shown that two separate condensates that expand into each other have clear interference effects.

. It was also shown that parts of the BEC could be dropped out and fall in the field of gravity.

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References

http://www.phys.ufl.edu/courses/phy4523/spring12/Sample%201.pdf

http://www.colorado.edu/physics/2000/bec/what_is_it.html

http://www.nobelprize.org/nobel_prizes/physics/laureates/2001/popular.html

https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate

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