Confined to One Dimension

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Science  24 Jun 2005:
Vol. 308, Issue 5730, pp. 1845
DOI: 10.1126/science.308.5730.1845a

In most instances, atoms in free space, either in the gas or liquid phase, can bind to form molecules only if the scattering length between the atoms is positive—that is, if the atoms attract. When the scattering length is negative, the atoms repel each other, and molecule formation does not occur. In the case of cold atoms, the scattering length can be tuned between positive and negative values by an external magnetic field.

Moritz et al. show that confining the atoms to a one-dimensional optical trap gives rise to quite different behavior. The reduced dimensionality in which the atoms move strongly affects the two-particle physics that subsequently determines the scattering length. They find two-particle bound molecular states irrespective of the field-tuned scattering length. This work illustrates the power of cold atoms to provide a tunable system that describes and mirrors the behavior of complex solid-state systems in which the analysis may not be as tractable. — ISO

Phys. Rev. Lett. 94, 210401 (2005).

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