Browsing by Author "Welford, C."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Phase coherence and superfluid-insulator transition in a disordered Bose-Einstein condensate
    (American Physical Society, 2008) Chen, Yong P.; Hitchcock, J.; Dries, D.; Junker, M.; Welford, C.; Hulet, R.G.; Rice Quantum Institute; Richard E. Smalley Institute for Nanoscale Science and Technology
    We have studied the effects of a disordered optical potential on the transport and phase coherence of a Bose-Einstein condensate (BEC) of L7i atoms. At moderate disorder strengths (VD), we observe inhibited transport and damping of dipole excitations, while in time-of-flight images, random but reproducible interference patterns are observed. In situ images reveal that the appearance of interference is correlated with density modulation, without complete fragmentation. At higher VD, the interference contrast diminishes as the BEC fragments into multiple pieces with little phase coherence.
  • Thumbnail Image
    Item
    Photoassociation of a Bose-Einstein Condensate near a Feshbach Resonance
    (American Physical Society, 2008) Junker, M.; Dries, D.; Welford, C.; Hitchcock, J.; Chen, Y.P.; Hulet, R.G.; Rice Quantum Institute
    We measure the effect of a magnetic Feshbach resonance (FR) on the rate and light-induced frequency shift of a photoassociation resonance in ultracold Li7. The photoassociation-induced loss-rate coefficient Kp depends strongly on magnetic field, varying by more than a factor of 10?4 for fields near the FR. At sufficiently high laser intensities, Kp for a thermal gas decreases with increasing intensity, while saturation is observed for the first time in a Bose-Einstein condensate. The frequency shift is also strongly field dependent and exhibits an anomalous blueshift for fields just below the FR.