Overlapping Bose-Einstein Condensates of \(^{23}\)Na and \(^{133}\)Cs

We report on the creation of dual-species Bose-Einstein condensates (BECs) of \(^{23}\)Na atoms and \(^{133}\)Cs atoms. We demonstrate sympathetic cooling of Cs with Na in a magnetic quadrupole trap and a crossed optical dipole trap, leading to Na BECs with \(8 \times 10^5\) atoms and Cs BECs with \(3.5 \times 10^4\) atoms. Investigating cross-thermalization and lifetimes of the mixture, we find that the Na and Cs BECs are miscible and overlapping, interacting with a moderate interspecies scattering length of \(18(4)\,a_0\) at \(23\,\)G and \(29(4)\,a_0\) at \(894\,\)G and coexisting for tens of seconds. Overlapping condensates of Na and Cs offer new possibilities for many-body physics with ultracold bosonic mixtures and constitute an ideal starting point for the creation of ultracold ensembles of NaCs ground state molecules.