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Observation of a 2D Bose Gas: From Thermal to Quasicondensate to Superfluid

2009; American Physical Society; Volume: 102; Issue: 17 Linguagem: Inglês

10.1103/physrevlett.102.170401

1092-0145

Pierre Cladé, Changhyun Ryu, Anand Ramanathan, Kristian Helmerson, William H. Phillips,

Strong Light-Matter Interactions

We present experimental results on a Bose gas in a quasi-2D geometry near the Berezinskii, Kosterlitz and Thouless (BKT) transition temperature. By measuring the density profile, \textit{in situ} and after time of flight, and the coherence length, we identify different states of the gas. In particular, we observe that the gas develops a bimodal distribution without long range order. In this state, the gas presents a longer coherence length than the thermal cloud; it is quasi-condensed but is not superfluid. Experimental evidence indicates that we observe the superfluid transition (BKT transition).