Bose-Einstein condensation and cooling to superlow temperatures
Can a dilute gas of atoms be cooled and compressed into a single, coherent quantum state (a Bose-Einstein condensate), and how well does phase-transition theory describe such ultracold systems?
History and references
Settled in 1995 by Cornell & Wieman and Ketterle (BEC, Nobel Prize 2001); Chu, Cohen-Tannoudji, Phillips (laser cooling, Nobel Prize 1997).
Ginzburg's problem #6 grouped second-order phase transitions with laser cooling to superlow temperatures and Bose-Einstein condensation (BEC) in gases. By the time his paper appeared, both laser cooling (Nobel 1997) and BEC in dilute atomic vapors (achieved 1995 by Cornell/Wieman with rubidium and by Ketterle with sodium, Nobel 2001) were already accomplished, and Ginzburg discusses them as recent triumphs rather than open puzzles; the general theory of continuous phase transitions (the renormalization group, Wilson's Nobel Prize 1982) likewise predated his paper. Since 1999 BEC has become a mature subfield (atom lasers, BEC-BCS crossover, quantum simulation with cold-atom lattices).
Cool a cloud of atoms enough and every one of them falls into exactly the same quantum wavefunction, so that a whole gas behaves as a single giant matter wave.
References
- What problems of physics and astrophysics seem now to be especially important and interesting (thirty years later, already on the verge of the XXI century)?, V L Ginzburg, Physics-Uspekhi 42 (4) 353-373, 1999
- Observation of Bose-Einstein Condensation in a Dilute Atomic Vapor, M. H. Anderson, J. R. Ensher, M. R. Matthews, C. E. Wieman, E. A. Cornell, Science 269, 198, 1995
- The Nobel Prize in Physics 2001, NobelPrize.org press release, 2001
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