Phase fluctuations in one-dimensional quasi-condensates on an atom chip

Full text: The intrinsic elongated geometry of wire traps on an atom chip provides direct access to ultra-cold one-dimensional systems. In contrast to the three-dimensional case, one- dimensional ultra-cold Bose gases do not exhibit long-range order. The respective phase fluctuations are observed in interference experiments with split one-dimensional Bose-Einstein condensates, using radio-frequency induced double well potentials. In the presented experiment, we investigate the ground state of two tunnel-coupled one-dimensional Bose gases of 87Rb. The ability to easily change the splitting in the double well potential allows studying the effect of different coupling strength on the relative phase between the atomic clouds. In agreement with theory the experiments verify that in this equilibrium system a finite coherence between the Bose-Einstein condensates depending on the coupling remains. (author)