Love and Hate Between Atoms on a Wire
24 July 2003 Atomic correlations are like human relations. Often, you either love someone or hate them. Depending on this, you may try to be close to loved ones and avoid those you hate. Now we can tell exactly how much 'like' or 'dislike' atoms have for each other when confined to a wire-like waveguide at ultra-low temperatures, thanks to an international team of researchers at: ARC Centre of Excellence for Quantum-Atom Optics, The University of Queensland, Australia; FOM Institute for Atomic and Molecular Physics, The Netherlands; and Ecole Normale Superieure, France [K.V. Kheruntsyan, D.M. Gangardt, P.D. Drummond and G.V. Shlyapnikov, Phys. Rev. Lett. 91 040403 (2003)]. In technical terms, the theoretical work studied spatial pair correlations of a gas of purely bosonic (integer spin) atoms with repulsive interactions. When confined to a nearly one-dimensional environment, with "frozen" transverse motion, such a gas shows a remarkable physics not encountered previously. In three dimensions, bosonic atoms undergo Bose-Einstein condensation, with all the atoms spread out in a quantum wave like a laser. However, a one-dimensional Bose gas can have atoms trying to bunch together, which occurs at high densities, or even 'fermionic' properties, with atoms trying to avoid each other. Only in an intermediate regime does the gas show coherence properties that are similar to those of photons in a laser light. Despite the fact that this type of problem was first treated in the 60's, no exact pair correlations at finite temperature have been calculated in 40 years. Quantum many-body systems at arbitrary temperatures and couplings normally require supercomputers to analyse their behaviour. Instead, the rigorous theory employed by the team from Australia, The Netherlands and France uses a simple combination of mathematical ideas - without supercomputers. These predictions of drastic changes with temperature and density should be testable in upcoming experiments in the near future. Possible applications are to the studies of coherence properties of atom lasers, high-precision interferometry, development of `atom-chip' devices, and sensitive measures for identifying the regime of finite-temperature 'fermionization'. Related links and media coverage:  UQ News
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Peter Drummond (left) and Karen Kheruntsyan (right) in the 
physics.uq.edu.au)