We investigate flow properties of immiscible Bose-Einstein condensates composed of two different Zeeman spin states of 87Rb. Spatially overlapping two condensates in the optical trap are prepared by application of a resonant radio frequency pulse, an
d then the magnetic field gradient is applied in order to produce the atomic flow. We find that the spontaneous multiple domain formation arising from the immiscible nature drastically changes the fluidity. The homogeneously overlapping condensates readily separate under the magnetic field gradient, and they form stable configuration composed of the two layers. In contrast, the relative flow between two condensates are largely suppressed in the case where the magnetic field gradient is applied after spontaneous domain formation.
We generate spin currents in an $^{87}$Rb spin-2 Bose-Einstein condensate by application of a magnetic field gradient. The spin current destroys the spin polarization, leading to a sudden onset of two-body collisions. In addition, the spin coherence,
as measured by the fringe contrast using Ramsey interferometry, is reduced drastically but experiences a weak revival due to in-trap oscillations. The spin current can be controlled using periodic $pi$ pulses (bang-bang control), producing longer spin coherence times. Our results show that spin coherence can be maintained even in the presence of spin currents, with applications to quantum sensing in noisy environments.
We report the spin texture formation resulting from the magnetic dipole-dipole interaction in a spin-2 $^{87}$Rb Bose-Einstein condensate. The spinor condensate is prepared in the transversely polarized spin state and the time evolution is observed u
nder a magnetic field of 90 mG with a gradient of 3 mG/cm using Stern-Gerlach imaging. The experimental results are compared with numerical simulations of the Gross-Pitaevskii equation, which reveals that the observed spatial modulation of the longitudinal magnetization is due to the spin precession in an effective magnetic field produced by the dipole-dipole interaction. These results show that the dipole-dipole interaction has considerable effects even on spinor condensates of alkali metal atoms.
We demonstrate detection of a weak alternate-current magnetic field by application of the spin echo technique to F = 2 Bose-Einstein condensates. A magnetic field sensitivity of 12 pT/Hz^1/2 is attained with the atom number of 5*10^3 at spatial resol
ution of 99 mu m^2. Our observations indicate magnetic field fluctuations synchronous with the power supply line frequency. We show that this noise is greatly suppressed by application of a reverse phase magnetic field. Our technique is useful in order to create a stable magnetic field environment, which is an important requirement for atomic experiments which require a weak bias magnetic field.
