%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 %0 Journal Article %J Physical Review Letters %D 2009 %T Number Fluctuations and Energy Dissipation in Sodium Spinor Condensates %A Yingmei Liu %A Eduardo Gomez %A Stephen E. Maxwell %A Lincoln D. Turner %A Eite Tiesinga %A Paul D. Lett %X We characterize fluctuations in atom number and spin populations in F=1 sodium spinor condensates. We find that the fluctuations enable a quantitative measure of energy dissipation in the condensate. The time evolution of the population fluctuations shows a maximum. We interpret this as evidence of a dissipation-driven separatrix crossing in phase space. For a given initial state, the critical time to the separatrix crossing is found to depend exponentially on the magnetic field and linearly on condensate density. This crossing is confirmed by tracking the energy of the spinor condensate as well as by Faraday rotation spectroscopy. We also introduce a phenomenological model that describes the observed dissipation with a single coefficient. %B Physical Review Letters %V 102 %8 2009/6/5 %G eng %U http://arxiv.org/abs/0906.2110v1 %N 22 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.102.225301 %0 Journal Article %J Physical Review Letters %D 2009 %T Quantum Phase Transitions and Continuous Observation of Spinor Dynamics in an Antiferromagnetic Condensate %A Yingmei Liu %A Sebastian Jung %A Stephen E. Maxwell %A Lincoln D. Turner %A Eite Tiesinga %A Paul. D. Lett %X Condensates of spin-1 sodium display rich spin dynamics due to the antiferromagnetic nature of the interactions in this system. We use Faraday rotation spectroscopy to make a continuous and minimally destructive measurement of the dynamics over multiple spin oscillations on a single evolving condensate. This method provides a sharp signature to locate a magnetically tuned separatrix in phase space which depends on the net magnetization. We also observe a phase transition from a two- to a three-component condensate at a low but finite temperature using a Stern-Gerlach imaging technique. This transition should be preserved as a zero-temperature quantum phase transition. %B Physical Review Letters %V 102 %8 2009/3/23 %G eng %U http://arxiv.org/abs/0902.3189v1 %N 12 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.102.125301