Abstract
We have realized Bose-Einstein condensation (BEC) of 87Rb in the F=2, m_F=2 hyperfine substate in a hybrid trap, consisting of a quadrupole magnetic field and a single optical dipole beam. The symmetry axis of the quadrupole magnetic trap coincides with the optical beam axis, which gives stronger axial confinement than previous hybrid traps. After loading 2x10^6 atoms at 14 muK from a quadrupole magnetic trap into the hybrid trap, we perform efficient forced evaporation and reach the onset of BEC at a temperature of 0.5 muK and with 4x10^5 atoms. We also obtain thermal clouds of 1x10^6 atoms below 1 muK in a pure single beam optical dipole trap, by ramping down the magnetic field gradient after evaporative cooling in the hybrid trap.
Highlights
The experimental realization of Bose-Einstein condensates (BEC) of dilute atomic gases [1,2] is most often based on laser cooling and subsequent evaporative cooling in magnetic or optical dipole traps, or both, in either a sequential or combined way
In all these previous hybrid traps the symmetry axis of the quadrupole magnetic trap (QMT) is placed vertically, while the optical dipole trap (ODT) is in the horizontal plane, and forced evaporative cooling in the QMT is done by RF radiation
Our coarse alignment is done using in-situ absorption images to locate the positions of the hybrid trap and the QMT
Summary
The experimental realization of Bose-Einstein condensates (BEC) of dilute atomic gases [1,2] is most often based on laser cooling and subsequent evaporative cooling in magnetic or optical dipole traps, or both, in either a sequential or combined way. A simple approach to achieve BEC is a hybrid trap that consists of a single beam optical dipole trap (ODT) and a quadrupole magnetic trap (QMT) [3]. This hybrid trap combines the most simple magnetic trap and optical dipole trap in a way that one benefits from their individual strengths, i.e. a large trap volume to capture the laser-cooled cloud of atoms, tight confinement and efficient evaporation, while minimizing their weaknesses, i.e. Majorana spin-flip losses in a QMT and a small trap volume of an ODT.
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