Observation of interspecies Feshbach resonances in an ultracold Rb-Cs mixture

TL;DR

This paper reports the discovery of 25 interspecies Feshbach resonances in an ultracold Rb-Cs mixture, revealing complex scattering behavior and aiding the formation of ultracold heteronuclear molecules.

Contribution

It provides the first comprehensive observation of interspecies Feshbach resonances in Rb-Cs, highlighting the role of partial waves and coupling mechanisms in ultracold scattering.

Findings

23 resonances in the lowest spin channel

2 resonances in a higher channel

Rich Feshbach spectrum indicating complex scattering dynamics

Abstract

We report on the observation of interspecies Feshbach resonances in an ultracold, optically trapped mixture of Rb and Cs atoms. In a magnetic field range up to 300 G we find 23 interspecies Feshbach resonances in the lowest spin channel and 2 resonances in a higher channel of the mixture. The extraordinarily rich Feshbach spectrum suggests the importance of different partial waves in both the open and closed channels of the scattering problem along with higher-order coupling mechanisms. Our results provide, on one hand, fundamental experimental input to characterize the Rb-Cs scattering properties and, on the other hand, identify possible starting points for the association of ultracold heteronuclear RbCs molecules.