Hung-Wen Cho

Dual-species Bose-Einstein condensate of 87Rb and 133Cs.

We report the formation of a dual-species Bose-Einstein condensate of 87Rb and 133Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of 133Cs via elastic collisions with 87Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to 2×104 atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the 87Rb during the cooling, we create single-species 133Cs condensates of up to 6×104 atoms.

Equilibrium solutions for immiscible two-species Bose-Einstein condensates in perturbed harmonic traps

We investigate the mean-field equilibrium solutions for a two-species immiscible Bose-Einstein condensate confined by a harmonic confinement with additional linear perturbations. We observe a range of equilibrium density structures, including ball and shell formations and axially or radially separated states, with a marked sensitivity to the potential perturbations and the relative atom number in each species. Incorporation of linear trap perturbations, albeit weak, are found to be essential to match the range of equilibrium density profiles observed in a recent 87Rb-133Cs Bose-Einstein condensate experiment [McCarron et al., Phys. Rev. A 84 011603(R) (2011)]. Our analysis of this experiment demonstrates that sensitivity to linear trap perturbations is likely to be an important factor in interpreting the results of similar experiments in the future.

Feshbach spectroscopy of an ultracold mixture of Rb-85 and Cs-133.

We report the observation of interspecies Feshbach resonances in an optically trapped mixture of 85Rb and 133Cs. We measure nine resonances in the lowest spin channel for a magnetic field range from 0 to 700 G and show that they are in good agreement with coupled-channel calculations. The interspecies background scattering length is close to zero over a large range of magnetic fields, permitting the sensitive detection of Feshbach resonances through interspecies thermalization. Our results confirm the quality of the Rb-Cs potential curves [ Phys. Rev. A 85 032506 (2012)] and offer promising starting points for the production of ultracold polar molecules.

Feshbach resonances in ultracold 85 Rb

We present 17 experimentally confirmed Feshbach resonances in optically trapped 85Rb. Seven of the resonances are in the ground-state channel (f,mf)=(2,+2)+(2,+2) and nine are in the excited-state channel (2,−2)+(2,−2). We find a wide resonance at high field in each of the two channels, offering possibilities for the formation of larger 85Rb condensates and studies of few-body physics. A detailed coupled-channel analysis is presented to characterize the resonances and also provides an understanding of the inelastic losses observed in the excited-state channel. In addition we have confirmed the existence of one narrow resonance in a (2,+2)+(3,+3) spin mixture.

Feshbach resonances in ultracold 85Rb.

We present 17 experimentally confirmed Feshbach resonances in optically trapped 85Rb. Seven of the resonances are in the ground-state channel (f,mf)=(2,+2)+(2,+2) and nine are in the excited-state channel (2,−2)+(2,−2). We find a wide resonance at high field in each of the two channels, offering possibilities for the formation of larger 85Rb condensates and studies of few-body physics. A detailed coupled-channel analysis is presented to characterize the resonances and also provides an understanding of the inelastic losses observed in the excited-state channel. In addition we have confirmed the existence of one narrow resonance in a (2,+2)+(3,+3) spin mixture.

Production of optically trappedRbCs87Feshbach molecules

We report the production of Feshbach molecules in a crossed-beam dipole trap. A mixture of and is cooled close to quantum degeneracy before an interspecies Feshbach resonance at 197 G is used to associate up to molecules with a temperature of nK. The molecules are confined in the dipole trap with a lifetime of 0.21(1) s, long enough for future experiments exploring optical transfer to the absolute ground state. We have measured the magnetic moment of the Feshbach molecules in a magnetic bias field range between 181 and 185 G to demonstrate the ability to control the character of the molecular state. In addition, we have performed Feshbach spectroscopy in a field range from 0 to 1200 G and located three previously unobserved resonances at high magnetic fields.

Production of optically trapped Feshbach molecules.

We report the production of Feshbach molecules in a crossed-beam dipole trap. A mixture of and is cooled close to quantum degeneracy before an interspecies Feshbach resonance at 197 G is used to associate up to molecules with a temperature of nK. The molecules are confined in the dipole trap with a lifetime of 0.21(1) s, long enough for future experiments exploring optical transfer to the absolute ground state. We have measured the magnetic moment of the Feshbach molecules in a magnetic bias field range between 181 and 185 G to demonstrate the ability to control the character of the molecular state. In addition, we have performed Feshbach spectroscopy in a field range from 0 to 1200 G and located three previously unobserved resonances at high magnetic fields.

Production of optically trapped

We report the production of Feshbach molecules in a crossed-beam dipole trap. A mixture of and is cooled close to quantum degeneracy before an interspecies Feshbach resonance at 197 G is used to associate up to molecules with a temperature of nK. The molecules are confined in the dipole trap with a lifetime of 0.21(1) s, long enough for future experiments exploring optical transfer to the absolute ground state. We have measured the magnetic moment of the Feshbach molecules in a magnetic bias field range between 181 and 185 G to demonstrate the ability to control the character of the molecular state. In addition, we have performed Feshbach spectroscopy in a field range from 0 to 1200 G and located three previously unobserved resonances at high magnetic fields.

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We present 17 experimentally confirmed Feshbach resonances in optically trapped 85Rb. Seven of the resonances are in the ground-state channel (f,mf)=(2,+2)+(2,+2) and nine are in the excited-state channel (2,−2)+(2,−2). We find a wide resonance at high field in each of the two channels, offering possibilities for the formation of larger 85Rb condensates and studies of few-body physics. A detailed coupled-channel analysis is presented to characterize the resonances and also provides an understanding of the inelastic losses observed in the excited-state channel. In addition we have confirmed the existence of one narrow resonance in a (2,+2)+(3,+3) spin mixture.