Studying a dual-species BEC with tunable interactions

TL;DR

This paper demonstrates controllable spatial separation in a dual-species Bose-Einstein condensate of rubidium isotopes, showing how tunable interactions affect their miscibility, with improved experimental capabilities for creating large condensates.

Contribution

It introduces a method to control the miscibility of dual-species BECs using Feshbach resonances, and reports the creation of larger condensates than previously achieved.

Findings

Observation of spatial separation indicating immiscibility

Tuning of interactions via Feshbach resonance alters miscibility

Creation of larger $^{85}$Rb condensates with up to 8×10^4 atoms

Abstract

We report on the observation of controllable spatial separation in a dual-species Bose-Einstein condensate (BEC) with $^{85}$Rb and $^{87}$Rb. Interparticle interactions between the different components can change the miscibility of the two quantum fluids. In our experiments, we clearly observe the immiscible nature of the two simultaneously Bose-condensed species via their spatial separation. Furthermore the $^{85}$Rb Feshbach resonance near 155 G is used to change them between miscible and immiscible by tuning the $^{85}$Rb scattering length. Our apparatus is also able to create $^{85}$Rb condensates with up to $8\times10^4$ atoms which represents a significant improvement over previous work.