Interspecies thermalization in an ultracold mixture of Cs and Yb in an optical trap

Abstract

We present measurements of interspecies thermalization between ultracold samples of $^{133}\mathrm{Cs}$ and either $^{174}\mathrm{Yb}$ or $^{170}\mathrm{Yb}$. The two species are trapped in a far-off-resonance optical dipole trap and $^{133}\mathrm{Cs}$ is sympathetically cooled by Yb. We extract effective interspecies thermalization cross sections by fitting the thermalization measurements to a kinetic model, giving ${\ensuremath{\sigma}}_{\mathrm{Cs}^{174}\mathrm{Yb}}=\left(5\ifmmode\pm\else\textpm\fi{}2\right)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}$ and ${\ensuremath{\sigma}}_{\mathrm{Cs}^{170}\mathrm{Yb}}=\left(18\ifmmode\pm\else\textpm\fi{}8\right)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}$. We perform quantum scattering calculations of the thermalization cross sections and optimize the CsYb interaction potential to reproduce the measurements. We predict scattering lengths for all isotopic combinations of Cs and Yb. We also demonstrate the independent production of $^{174}\mathrm{Yb}$ and $^{133}\mathrm{Cs}$ Bose-Einstein condensates using the same optical dipole trap, an important step toward the realization of a quantum-degenerate mixture of the two species.