Three-body recombination near the d -wave resonance in ultracold Rb85−Rb87 mixtures

Abstract

In this study, we investigate the three-body recombination (TBR) rates on both sides of the interspecies $d$-wave Feshbach resonance in the $^{85}\mathrm{Rb}$ -$^{87}\mathrm{Rb}\ensuremath{-}^{87}\mathrm{Rb}$ system using the $R$-matrix propagation method in the hyperspherical coordinate frame. Our calculations are based on the Lennard-Jones model potential for the Rb-Rb interaction. Two different mechanisms of recombination-rate enhancement for positive and negative $^{85}\mathrm{Rb}$ -$^{87}\mathrm{Rb} d$-wave scattering lengths are analyzed. On the positive-scattering-length side, recombination-rate enhancement occurs due to the existence of three-body shape resonance, while on the negative-scattering-length side, the coupling between the lowest entrance channel and the highest recombination channel is crucial to the appearance of the enhancement. In addition, our study shows that the intraspecies interaction has a significant role in determining the emergence of recombination-rate enhancements. Compared to the case in which the three pairwise interactions are in $d$-wave resonance, when the $^{87}\mathrm{Rb}\ensuremath{-}^{87}\mathrm{Rb}$ interaction is near the $d$-wave resonance, the values of the interspecies scattering length that produce the recombination enhancement shift. In particular, when the $^{87}\mathrm{Rb}\ensuremath{-}^{87}\mathrm{Rb}$ interaction is away from the $d$-wave resonance, the enhancement disappears on the side with negative interspecies scattering length.