A compact experimental machine for studying tunable Bose–Bose superfluid mixtures

Abstract

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

Stochastic dynamics of a few sodium atoms in presence of a cold potassium cloud

“…In " Full counting statistics of sodium " section, we leverage the single atom counting resolution of sodium to extract the full counting statistics of atom load and loss events. In contrast to previous experiments with sodium and potassium 37 , 40 , we operate at such low atomic densities that the presence of the potassium cloud has no measurable effect on the counting statistics of sodium. In " Outlook " section, we end with an outlook of the next steps for the experimental platform.…”

Miscibility Regimes in a 23Na–39K Quantum Mixture

“…A complete description of the experimental setup and experimental sequence for producing a Bose-Einstein condensate of 23 Na atoms is described in [40]. Here, we present a short description of the system giving the experimental parameters relevant for the simulations performed later in this Section.…”

“…Briefly, sodium and potassium atoms coming from independent two-dimensional magneto-optical traps (2D-MOTs) [48,49] are combined in a common vacuum chamber where they will be trapped and further cooled in a three-dimensional MOT (3D-MOT). Due to the strong interspecies losses present in the Na-K mixture [40,50], the operation of an intial two-color MOT is not the best alternative in our experiment. Instead, we chose to favor the minority species (potassium) during the MOT phase, starting the MOT sequence with the loading of a single species MOT of 39 K until it reaches the saturation value (∼20 s).…”

“…In this work, we perform numerical simulations of the ground-state of a two-component quantum mixture of 23 Na and 39 K atoms for different interaction strengths, according to the relevant Feshbach resonances for magnetic fields in the range of 95-117 G [14,39], in order to show the realistic miscibility regimes accessible in the experimental setup being developed in our laboratory [40] in the presence of gravity. We explore the effect of changing the number of atoms of the minority species ( 39 K), thereby changing the atom number ratio η, and calculating the spatial overlap between the atomic clouds as a quantity able to characterize the change in the miscibility regime of the system.…”

The gray molasses cooling technique for optimizing the temperature of 39K atoms

“…In this chapter we will describe in a briefly way our compact and versatile NaK experiment built by our group [Castilho et al,48 Penafiel et al 49 ], with the finality to obtain the best performace of Na-K bosonic mixtures.…”