Observation of interspecies Feshbach resonances in an ultracold $^{39}$K-$^{133}$Cs mixture and refinement of interaction potentials

TL;DR

This study reports the detection of interspecies Feshbach resonances in ultracold $^{39}$K-$^{133}$Cs mixtures, refining interaction models and enabling control of interactions and molecule formation.

Contribution

The paper presents the first observation of interspecies Feshbach resonances in $^{39}$K-$^{133}$Cs and improves interaction potentials through experimental data fitting.

Findings

Identification of multiple Feshbach resonances in different spin states.

Refined interaction potentials matching observed resonances.

Potential for tuning interactions and creating ultracold KCs molecules.

Abstract

We observe interspecies Feshbach resonances due to s-wave bound states in ultracold $^{39}$K-$^{133}$Cs scattering for three different spin mixtures. The resonances are observed as joint atom loss and heating of the K sample. We perform least-squares fits to obtain improved K-Cs interaction potentials that reproduce the observed resonances, and carry out coupled-channel calculations to characterize the scattering and bound-state properties for $^{39}$K-Cs, $^{40}$K-Cs and $^{41}$K-Cs. Our results open up the possibilities of tuning interactions in K-Cs atomic mixtures and of producing ultracold KCs molecules.