%0 Journal Article %J Physical Review A %D 2011 %T Spatial separation in a thermal mixture of ultracold $^174$Yb and $^87$Rb atoms %A Florian Baumer %A Frank Münchow %A Axel Görlitz %A Stephen E. Maxwell %A Paul S. Julienne %A Eite Tiesinga %X We report on the observation of unusually strong interactions in a thermal mixture of ultracold atoms which cause a significant modification of the spatial distribution. A mixture of $^{87}$Rb and $^{174}$Yb with a temperature of a few $\mu$K is prepared in a hybrid trap consisting of a bichromatic optical potential superimposed on a magnetic trap. For suitable trap parameters and temperatures, a spatial separation of the two species is observed. We infer that the separation is driven by a large interaction strength between $^{174}$Yb and $^{87}$Rb accompanied by a large three-body recombination rate. Based on this assumption we have developed a diffusion model which reproduces our observations. %B Physical Review A %V 83 %8 2011/4/21 %G eng %U http://arxiv.org/abs/1104.1722v1 %N 4 %! Phys. Rev. A %R 10.1103/PhysRevA.83.040702