We present a compact and versatile experimental system for producing Bose-Bose superfluid mixtures composed of sodium and potassium atoms. The compact design combines the necessary ultra-high vacuum enviroment for ultracold atom experiments with efficient atomic fluxes by using two-dimensional magneto-optical traps as independent source of atoms. We demonstrate the performance of this new machine by producing a Bose-Einstein condensate of 23 Na with ∼ 1 × 10 6 atoms. The tunability of Na-K bosonic mixtures is particularly interesting for studies regarding the nucleation of vortices and quantum turbulence. In this direction, the large optical access of the science chamber along the vertical direction provides the conditions to implement high resolution optical setups for imaging and rotating the condensate with a stirring beam. We show the nucleation of a vortex lattice with up to 14 vortices in the 23 Na BEC, attesting the efficiency of the experimental apparatus in studying the dynamics of vortices. * patricia.castilho@usp.br; Current address: Laboratoire Kastler Brossel, Collège
We report the observation of the controlled expansion of a two-dimensional quantum gas confined onto a curved shell-shaped surface. We start from the ellipsoidal geometry of a dressed quadrupole trap and introduce a novel gravity compensation mechanism enabling to explore the full ellipsoid. The zero-point energy of the transverse confinement manifests itself by the spontaneous emergence of an annular shape in the atomic distribution. The experimental results are compared with the solution of the three-dimensional Gross-Pitaevskii equation and with a two-dimensional semi-analytical model. This work evidences how a hidden dimension can affect dramatically the embedded low-dimensional system by inducing a change of topology.
The effects of miscibility in interacting two-component classical fluids are relevant in a broad range of daily applications. When considering quantum systems, two-component Bose–Einstein condensates provide a well-controlled platform where the miscible–immiscible phase transition can be completely characterized. In homogeneous systems, this phase transition is governed only by the competition between intra- and inter-species interactions. However, in more conventional experiments dealing with trapped gases, the pressure of the confinement increases the role of the kinetic energy and makes the system more miscible. In the most general case, the miscibility phase diagram of unbalanced mixtures of different atomic species is strongly modified by the atom number ratio and the different gravitational sags. Here, we numerically investigate the ground-state of a 23Na–39K quantum mixture for different interaction strengths and atom number ratios considering realistic experimental parameters. Defining the spatial overlap between the resulting atomic clouds, we construct the phase diagram of the miscibility transition which could be directly measured in real experiments.
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