@article {1301, title = {Spatial separation in a thermal mixture of ultracold $^{174}$Yb and $^{87}$Rb atoms }, journal = {Physical Review A}, volume = {83}, year = {2011}, month = {2011/4/21}, abstract = { 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. }, doi = {10.1103/PhysRevA.83.040702}, url = {http://arxiv.org/abs/1104.1722v1}, author = {Florian Baumer and Frank M{\"u}nchow and Axel G{\"o}rlitz and Stephen E. Maxwell and Paul S. Julienne and Eite Tiesinga} } @article {1298, title = {Number Fluctuations and Energy Dissipation in Sodium Spinor Condensates}, journal = {Physical Review Letters}, volume = {102}, year = {2009}, month = {2009/6/5}, abstract = { 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. }, doi = {10.1103/PhysRevLett.102.225301}, url = {http://arxiv.org/abs/0906.2110v1}, author = {Yingmei Liu and Eduardo Gomez and Stephen E. Maxwell and Lincoln D. Turner and Eite Tiesinga and Paul D. Lett} } @article {1302, title = {Quantum Phase Transitions and Continuous Observation of Spinor Dynamics in an Antiferromagnetic Condensate }, journal = {Physical Review Letters}, volume = {102}, year = {2009}, month = {2009/3/23}, abstract = { 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. }, doi = {10.1103/PhysRevLett.102.125301}, url = {http://arxiv.org/abs/0902.3189v1}, author = {Yingmei Liu and Sebastian Jung and Stephen E. Maxwell and Lincoln D. Turner and Eite Tiesinga and Paul. D. Lett} }