Monday, December 29, 2008

The coldest transistor ever !

This is a brief review of the paper published in Physical Review A.

An electronic transistor is a three-terminal, solid-state device, used to amplify a signal in electronic circuits. The three terminals are called - an emitter (E), a base(B) and a collector(C). Can we make a transistor out of a Bose-Einstein Condensate (BEC)? The answer is - YES ! A transistor can be designed by using a BEC in an asymmetric triple-well potential. Let's consider a triple-well potential with wells labeled - Left(L), Middle(M) and Right(R). The left well, L, has a lot of cold atoms in the BEC state, so it acts as an emitter (E). If there are no atoms or a very few atoms in the middle well, M, and no atoms in the right well, R, no atoms can tunnel through the middle well to reach the right well, which acts as collector(C). This is because of the mismatch of the chemical potential between the three wells. If the atomic population in M is increased to some value, there will be a large flux of atoms reaching R, tunelling through M. Because when the number of atoms are increased in M, the chemical potential rises due to the nonlinearity caused by atom-atom interactions, making tunnelling possible. Thus, M is analogous to the base of an electronic transistor. Thus by controlling the atomic population in M, the atomic population in R can be controlled/amplified. Hence, this system clearly shows a transistor-like behavior and is the coldest transitor ever as it functions at BEC temperature, which is some micro/nanoKelvins! A BEC transistor may prove to be useful in precision measurements.

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