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Non-equilibrium coherence dynamics in one-dimensional Bose gases

2007; Nature Portfolio; Volume: 449; Issue: 7160 Linguagem: Inglês

10.1038/nature06149

1476-4687

Sebastian Hofferberth, Igor Lesanovsky, Beate Fischer, Thorsten Schumm, Jörg Schmiedmayer,

Quantum many-body systems

This paper reports a direct experimental study of the coherence dynamics in both isolated and coupled degenerate one-dimensional (1D) Bose gases. Completely isolated 1D Bose gases exhibit coherence decay in excellent agreement with recent predictions. The coherence of two coupled 1D Bose gases decays to a finite value, analogous to the phase locking of two lasers by injection. Low-dimensional systems provide beautiful examples of many-body quantum physics1. For one-dimensional (1D) systems2, the Luttinger liquid approach3 provides insight into universal properties. Much is known of the equilibrium state, both in the weakly4,5,6,7 and strongly8,9 interacting regimes. However, it remains a challenge to probe the dynamics by which this equilibrium state is reached10. Here we present a direct experimental study of the coherence dynamics in both isolated and coupled degenerate 1D Bose gases. Dynamic splitting is used to create two 1D systems in a phase coherent state11. The time evolution of the coherence is revealed through local phase shifts of the subsequently observed interference patterns. Completely isolated 1D Bose gases are observed to exhibit universal sub-exponential coherence decay, in excellent agreement with recent predictions12. For two coupled 1D Bose gases, the coherence factor is observed to approach a non-zero equilibrium value, as predicted by a Bogoliubov approach13. This coupled-system decay to finite coherence is the matter wave equivalent of phase-locking two lasers by injection. The non-equilibrium dynamics of superfluids has an important role in a wide range of physical systems, such as superconductors, quantum Hall systems, superfluid helium and spin systems14,15,16. Our experiments studying coherence dynamics show that 1D Bose gases are ideally suited for investigating this class of phenomena.