Overlapping Bose-Einstein Condensates of $^{23}$Na and $^{133}$Cs

TL;DR

This paper reports the creation of dual-species Bose-Einstein condensates of sodium and cesium, demonstrating their coexistence, interactions, and potential for exploring many-body physics and ultracold molecules.

Contribution

It presents the first realization of overlapping Na and Cs BECs with detailed characterization of their interactions and stability.

Findings

Na and Cs BECs are miscible and overlapping.

Interspecies scattering lengths are moderate at different magnetic fields.

The mixture remains stable and coexists for tens of seconds.

Abstract

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.