arXiv:1508.04019 · Applied Physics B
Simple method for producing Bose–Einstein condensates of metastable helium using a single-beam optical dipole trap
Adonis Silva Flores, Hari Prasad Mishra, W. Vassen, Steven Knoop
Abstract
We demonstrate a simple scheme to reach Bose–Einstein condensation (BEC) of metastable triplet helium atoms using a single-beam optical dipole trap with moderate power of less than 3 W. Our scheme is based on RF-induced evaporative cooling in a quadrupole magnetic trap and transfer to a single-beam optical dipole trap that is located below the magnetic trap center. We transfer $$1\times 10^6$$ atoms into the optical dipole trap, with an initial temperature of $$14\,\upmu\hbox{K}$$ , and observe efficient forced evaporative cooling both in a hybrid trap, in which the quadrupole magnetic trap operates just below the levitation gradient, and in the pure optical dipole trap, reaching the onset of BEC with $$2\times 10^5$$ atoms and a pure BEC of $$5\times 10^4$$ atoms. Our work shows that a single-beam hybrid trap can be applied for a light atom, for which evaporative cooling in the quadrupole magnetic trap is strongly limited by Majorana spin-flips, and the very small levitation gradient limits the axial confinement in the hybrid trap.