Editor's Summary
15 June 2006
An unlikely union
In physics it is common for objects that attract each other to form stable bound states by lowering their energy. But under certain conditions, stable composite objects exist even for repulsive interactions. The creation of one such exotic bound state is reported this week. It consists of a pair of ultracold rubidium atoms in an optical lattice. The pairs are stable because two atoms sitting on a given site of an optical lattice with strong repulsive interactions cannot decay as they cannot convert their potential energy into kinetic energy, a phenomenon explained by the constraints of the Bose–Hubbard model for the structure of ultracold quantum gases.
News and Views: Quantum physics: United through repulsion
Mutually repulsive atoms placed at periodic intervals in a 'crystal of light' can, counterintuitively, be forced into stable couplings. That theoretical prediction has just seen experimental confirmation.
Leonardo Fallani and Massimo Inguscio
doi:10.1038/441820a
Letter: Repulsively bound atom pairs in an optical lattice
K. Winkler, G. Thalhammer, F. Lang, R. Grimm, J. Hecker Denschlag, A. J. Daley, A. Kantian, H. P. Büchler and P. Zoller
doi:10.1038/nature04918