Feshbach spectroscopy of an ultracold mixture of $^{85}$Rb and $^{133}$Cs

TL;DR

This study identifies and characterizes interspecies Feshbach resonances in an ultracold mixture of rubidium-85 and cesium-133, providing insights for creating ultracold polar molecules.

Contribution

First observation and measurement of interspecies Feshbach resonances in Rb-85 and Cs-133 mixture, validated by coupled-channel calculations.

Findings

14 interspecies Feshbach resonances observed

Interspecies background scattering length near zero

Results support potential curves for Rb-Cs interactions

Abstract

We report the observation of interspecies Feshbach resonances in an optically trapped mixture of $^{85}$Rb and $^{133}$Cs. We measure 14 interspecies features in the lowest spin channels for a magnetic field range from 0 to 700 G and show that they are in good agreement with coupled-channel calculations. The interspecies background scattering length is close to zero over a large range of magnetic fields, permitting the sensitive detection of Feshbach resonances through interspecies thermalisation. Our results confirm the quality of the Rb-Cs potential curves and offer promising starting points for the production of ultracold polar molecules.