Probing an interacting Bose gas in a quasi-two-dimensional trap

<p>A fluctuating regime associated with the Berenzinskii-Kosterlitz-Thouless (BKT) transition is studied in a two-dimensional system of near-degenerate bosons (87Rb atoms). Two imaging procedures, the in-situ imaging method and the focusing-imaging method, are implemented to image the coordinate-space and momentum-space density distributions. The scaled compressibility is extracted from the coordinate-space density distributions obtained from in-situ images. Comparing the measured compressibility to the prediction from our semiclassical mean-field model, an onset of a regime which is beyond the mean-field prediction is identified and first resolved at phase-space density nλ2 ≳ 3. Information about the coherence of the system is extracted from the momentum-space distributions obtained from the focusing images. The spatial extent of the coherence at a size of the high density region in the system only appears at a distinguishably higher phase-space density of nλ2 ≈ 8. Therefore, a very interesting regime that is beyond mean-field prediction, but not yet a quasicondensate, is identified. This regime, which does not exist in three dimensions, is a product of the enhanced interactions associated with reduced dimensionality.</p>
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University of Colorado Boulder
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