Observation of magnetic Feshbach resonances between Cs and ${}^{173}\mathrm{Yb}$

We report the observation of magnetic Feshbach resonances between ${}^{173}\mathrm{Yb}$ and ${}^{133}\mathrm{Cs}$. In a mixture of Cs atoms prepared in the $(f=3,m_f=3)$ state and unpolarized fermionic ${}^{173}\mathrm{Yb}$, we observe resonant atom loss due to two sets of magnetic Feshbach resonances around 622 and 702 G. Resonances for individual Yb nuclear spin components $m_{i,\mathrm{Yb}}$ are split by its interaction with the Cs electronic spin, which also provides the main coupling mechanism for the observed resonances. The observed splittings and relative resonance strengths are in good agreement with theoretical predictions from coupled-channel calculations.

Figure 1

Origin and detection of Feshbach resonances for $\mathrm{Cs}+{}^{173}\mathrm{Yb}$. (a),(b) Relative number of Cs atoms remaining after holding for 1 s at a variable magnetic field. Green (red) points show measurements performed with (without) ${}^{173}\mathrm{Yb}$ in the dipole trap. The normalized Cs number in the absence of ${}^{173}\mathrm{Yb}$ is offset for clarity. Solid lines are fitted sums of Voigt profiles, with the individual components shown in gray. (c),(d) Level crossings giving rise to the detected resonances for the individual spin states labeled by $m_{i,\mathrm{Yb}}$. Symbols indicate crossings fulfilling $\mathrm{\Delta }{m}_{i,\mathrm{Yb}}=-\mathrm{\Delta }{m}_f$. Faint dotted lines show the bound states without the shifts induced by mechanism II, in which case all resonances would occur at the same field. The vertical scale is $h\times 4\mathrm{MHz}$. (e) Relevant thresholds (purple lines) and bound-state energies (red lines) over the experimentally accessible field range. Vibrational levels that do not give rise to an observed resonance are truncated to low fields for clarity. Structure due to different values of $m_{i,\mathrm{Yb}}$ is not visible on the scale of (e).

Figure 2

Predicted normalized resonance widths $\overline{\mathrm{\Delta }}$ for the two observed sets of resonances with $\mathrm{\Delta }{m}_f=1$ and $\mathrm{\Delta }{m}_f=0$ [55]. For $\mathrm{\Delta }{m}_f=1$, only mechanism II contributes, while for $\mathrm{\Delta }{m}_f=0$, both mechanism I and mechanism II contribute.